OBJECTIVE To verify the efficacy and safety of Quxie Capsule () in patients with metastatic colorectal cancer (mCRC). METHODS The present study was a randomized, double-blind, placebo-controlled trial. Sixty patients with mCRC were randomized into two groups at a 1:1 ratio by sealed envelope. The treatment group received conventional therapy combined with Quxie Capsule for 3 months. The control group was treated with conventional therapy combined with placebo for 3 months. Main outcome measures were overall survival (OS) and progression-free survival (PFS). Subgroup analysis was performed according to age, right or left-sided disease, and second-line therapy to determine the differences in PFS and OS between the two groups. Patients were followed up every 3 months until Dec 31st 2016. RESULTS The median OS was 23 months in the treatment group [95% confidence interval (CI): 15-not calculated] vs. 14 months in the control group (95% CI: 11-22, P=0.060). The OS of the treatment group tended to be longer than that of the control group (P>0.05). In the subgroups of patients <65 years old, left-sided colon, and 2nd-line therapy, the treatment group showed a significant survival benefit compared with the control group (P=0.006, 0.038, 0.013, respectively). There were no significant differences between the two groups in PFS (P>0.05). Safety analysis showed no severe hematological toxicity or liver and renal function injury in the treatment group. CONCLUSIONS Quxie Capsule showed good safety and efficacy, and could prolong the OS of patients with mCRC. (Registration No. ChiCTR-IOR-16009733).