RNA synthetic biology, as a frontier interdisciplinary field, is driving the leap from fundamental research to precision medicine in life sciences through the engineered design of RNA components and the construction of genetic circuits. This paper aims to systematically outline the design principles, key technological breakthroughs, and biomedical applications of synthetic RNA genetic circuits. Building upon this foundation, it provides an in-depth analysis of current research bottlenecks and proposes future development directions. Commencing with a foundational role in the central dogma of RNA, this paper establishes a systematic classification framework for synthetic biology RNA components. At the cis-acting element level, it elaborates on how components such as riboswitches, RNA thermometers, and Toehold switches achieve precise gene expression regulation by responding to specific ligands, temperatures, or trigger RNAs through conformational changes. Concerning trans-acting elements, it delves into the molecular mechanisms of miRNA-mediated gene silencing, the high stability and “sponge-like adsorption” function conferred by the closed-loop structure of circRNA, the targeting role of siRNA within the RNAi pathway, and the targeting specificity of sgRNA within the CRISPR system. The paper emphasizes that rational design, sequence optimization, and chemical modifications can significantly enhance the performance and orthogonality of these natural elements. Secondly, the paper focuses on the design and optimization strategies for synthetic RNA regulatory modules. Taking miRNA-responsive circRNA switches as an example, it elucidates the principles of customized miRNA responsiveness. The engineering applications of circRNA are explored, introducing strategies for constructing functional RNA nanostructures via siRNA self-assembly. Building upon this, the paper emphasizes synthetic genetic circuits: from logical operations to resource allocation, enabling advanced cellular logic and functional regulation. For instance, by combining transcriptional cascade switches or utilizing the CRISPR-Cas13a system, an AND logic gate responsive to multiple miRNAs (such as miRNA-155 and miRNA-21) was constructed, significantly enhancing the specificity of disease diagnosis. Addressing the challenges of resource competition and expression noise faced by synthetic circuits within cells, this paper introduces computational models such as MIRELLA, with particular emphasis on the design of endogenous miRNA-based iFFLs. These advanced circuits, illustrated in this paper, have been successfully applied to real-time monitoring of cellular differentiation states and regulation of stem cell-directed differentiation. For cellular state detection and dynamic regulation, miRNA switches can be integrated with fluorescent systems to track differentiation statuses in real time via fluorescent signal changes. Synthetic genetic circuits, meanwhile, utilize endogenous miRNA logic integration alongside miSFITs technology to achieve state-specific protein regulation in human pluripotent stem cells, laying the groundwork for customized cellular control. This approach ingeniously harnesses intrinsic cellular regulatory mechanisms to buffer gene expression burdens, thereby enhancing circuit robustness. These advanced circuits, illustrated schematically herein, have been successfully applied to real-time monitoring of cellular differentiation states and regulation of stem cell-directed differentiation. At the therapeutic translation level, the paper systematically reviews application strategies for RNA technologies across multiple fields, including cancer, metabolic diseases, neurodegenerative diseases, cardiovascular diseases, regenerative medicine engineering, immunotherapy, and vaccine applications. For instance, in cancer treatment, specific killing of tumor cells is achieved by embedding targets for miRNAs specific to healthy cells within the genomes of oncolytic viruses (such as Zika virus). Within metabolic and degenerative diseases, LNP-delivered mRNA therapeutics and antisense oligonucleotide (ASO) technologies have demonstrated significant clinical progress. Finally, this paper highlights ongoing challenges in the field, including limited programmability of RNA elements, low in vivo delivery efficiency, and inadequate off-target risk assessment systems. It advocates for future integration of epigenomics and computational modelling to optimize element functionality, establishing an integrated “element-circuit-delivery” platform. Furthermore, leveraging single-cell sequencing and organoid technologies to develop a multidimensional safety assessment system is proposed to advance the deep integration and translation of RNA synthetic biology in personalized medicine. Consequently, RNA engineering has transcended single-dimensional regulation, evolving towards multi-layered, dynamic, and intelligent synthetic biological systems. Its deep integration with clinical needs will reshape disease diagnosis and treatment paradigms.