Objective:To explore the expression of breast cancer susceptibility gene 1 (BRCA1) in human colorectal cancer and its correlation with efifcacy of platinum-based chemotherapy. Methods:A total of 78 samples from patients with colorectal cancer and receiving platinum-based chemotherapy were selected, and meanwhile 14 cases of normal colonic mucosa samples were selected as a normal control, 12 cases of non-cancerous tissue in colorectal cancer samples were selected as a pericarcinorma control. The expression of BRCA1 in these tissues was detected using immunohistochemical S-P method, and all patients treated with drugs were followed-up for survival time. Results: The positive rate of BRCA1 expression in colorectal cancer tissue was 52.6%, signiifcantly lower than that in the control groups. BRCA1 expression was closely associated with histological differentiation degrees (χ2=14.16,P=0.001), but not with the age, gender, local inifltration, lymph node metastasis and TNM staging. Comparing with those with positive BRCA1 expression, the patients with negative BRCA1 expression after oxaliplatin-based chemotherapy had signiifcantly longer disease-free survival (DFS) (P=0.032). Conclusion:Application of oxaliplatin-based chemotherapy in the patients with negative BRCA1 expression can obtain the survival beneift, and the level of BRCA1 expression can be useful in the selection of chemotherapy regimens and evaluation of prognosis for patients with colorectal cancer after surgery.