Objective To inhibit the expression of BLM gene in the Huh7 hepatocarcinoma cell line by CRISPR/Cas9 technology and explore the biological effect on Huh7 cells after downregulation of BLM gene expression. Methods Bioinformatics analysis was conducted to examine the expression differences of the BLM gene in liver cancer tissues and adjacent tissues, as well as the correlation between BLM expression levels and the prognosis of liver cancer patients. The cell proliferation of BLM gene knockdown plasmid was detected by the CCK-8 method, and the cell cycle and apoptosis were detected by flow cytometry. The content of DNA damage marker γ-H2AX was detected by immunoblotting. The effect of expression of BRCA1, RAD51 and P53 proteins in cells was detected by immunoblotting. Results Bioinformatics analysis showed that the BLM gene was highly expressed in liver cancer, and the expression level of BLM was negatively correlated with the prognosis of liver cancer patients. The BLM gene knockout plasmid was transfected into Huh7 cells, puromycin was screened and monoclonal cultured. The cell line with significantly reduced BLM helicase (BLM-KD cell line) was verified by western blot, and the expression of BLM protein in this cell line decreased by 57.2% (P<0.05), the sequencing results showed that there were base changes at the target sites of BLM-KD cells. Compared with the normal group, cell proliferation in the BLM-KD group was significantly slowed down, showing a time-dependent (P<0.001). By flow cytometry, BLM-KD cells were found to have decreased G1 phase cells (P<0.001), increased G2 phase cells (P<0.05), and increased apoptosis rate (P<0.05) compared with control group. Immunofluorescence staining revealed that the content of the DNA damage marker γ-H2AX increased compared with the control group (P<0.05). Immunoblotting showed that BRCA1 expression was attenuated (P<0.05), RAD51 expression was attenuated (P＞0.05), and P53 expression was enhanced (P<0.001). Conclusion Knockdown of the BLM gene can inhibit the proliferation ability of liver cancer Huh7 cells and promote its apoptosis, which may be related to DNA damage repair and provides a basis for targeted gene therapy for liver cancer