β-actin gene is a kind of actin, in a variety of cells and tissues, β-actin gene expression is relatively stable [1], and β-actin gene in nuclear DNA has multiple copies, increased The detection rate of nuclear DNA [2], which is often used as an internal reference in PCR. In this experiment, the β-actin gene with good purity was obtained by PT-PCR, amplification, cloning, screening and PCR identification and restriction enzyme digestion of the RNA extracted from the mouse liver, which laid the foundation for the later experiment.