English: The widespread application of gene editing technology in crop improvement at present largely benefits from the emergence of the CRISPR/Cas9 system, which is derived from the immune system of bacteria and archaea. The CRISPR/Cas9 system was synthesized by connecting single-guide RNA (sgRNA) and Cas9. The sgRNA can bind to the target site after specific modification. The RuvC domain of Cas9 protein can cleave the DNA strand with protospacer-associated motif (PAM) sites, and the DNA strand complementary to sgRNA is cleaved by the HNH domain of Cas9 protein. The cutting site is near the PAM site.