Recombinant Cas9 protein derived from Streptococcus pyogenes is a protein that plays a key role in CRISPR/Cas9 system. It has endonuclease activity; Under the guidance of sgRNA, Cas9 protein can move to the target gene site, cut DNA accurately, and cause DNA double-strand breaks. Ubigene's HGC-27 cell line was constructed on the basis of wild-type HGC-27 cells by lentiviral transduction of the engineered Cas9 protein gene, which can stably express Cas9 protein for a long time. Using this cell, efficient gene knockout, knock-in and point mutation in HGC-27 cells can be achieved by only transfecting sgRNA or co-transfecting sgRNA and donor DNA. It can also be used for the construction of cell knockout library and easily solve the problem of Cas9 transfection difficulty.