MicroRNAs (miRNAs) are small non-coding RNAs which are essential for posttranscriptional gene regulation and have important roles in physiology and pathology. The researches on function of miRNA will be a focus in the future. Several animal models have been built by transgenic technology, making important contributions to our understanding of gene function at the whole scale. Recently, the number of transgenic animal models for microRNAs and construction strategies have been increasing and diversifying. Some roles of miRNA in tumor and cardiovascular disease have been revealed by transgenic animals. Transgenic animals are becoming a kind of powerful tool in microRNA researches.