The mutations in human disease-causing genes are predominantly caused by point mutations, with more than half of them being transitions between guanine (G) and adenine (A). Precise and efficient in situ repair of these mutations is the most ideal approach for the treatment of genetic diseases. Given that most point mutations are transitions between G and A, adenine base editors (ABEs) based on the CRISPR/Cas9 system, which convert A to G, are particularly important for repairing these mutations in the treatment of human genetic diseases. In recent years, ABEs have been continuously optimized, with both activity and fidelity being improved. Here we summarize the progress of ABEs, especially those key mutants developed during the process of ABE optimization. It also reflects on the existing defects in current ABEs. Additionally, the article reviews the clinical applications (including preclinical studies) of ABE. Overall, the article aims to provide references for the discovery and optimization of new ABEs and their applications.