Objective:To observe the efficacy and safety of teriprizumab combined with bevacizumab in above the second line treatment of high-level microsatellite instability (MSI-H) type metastatic colorectal cancer (mCRC) patients.Methods:From February 2019 to September 2019, 56 patients with MSI-H mCRC admitted to the Third Affiliated Hospital of Guangdong Medical University were selected and divided into control group and test group by random number table method, with 28 cases in each group. The control group was treated with bevacizumab, and the test group was treated with teriprizumab combined with bevacizumab. The objective response rate (ORR), disease control rate (DCR), progression-free survival, overall survival and incidence of adverse reactions were compared between the two groups.Results:The ORR and DCR of the test group were 60.71% (17/28) and 75.00% (21/28) respectively, higher than 28.57% (8/28) and 46.63% (13/28) of the control group, with statistically significant differences ( χ2=5.85, P=0.016; χ2=4.79, P=0.029). The median progression-free survival of patients in the control group and the test group were 3.5 months and 5.8 months respectively, with a statistically significant difference ( χ2=9.83, P=0.003). The median overall survival of patients in the control group and the test group were 12.1 months and 16.2 months respectively, with a statistically significant difference ( χ2=6.13, P=0.007). There were no significant diffe-rences in the incidences of hematological reaction (17.86% vs. 14.29%, χ2=0.13, P=0.716), cardiovascular injury (10.71% vs. 14.29%, χ2=0.16, P=0.686), liver and kidney function injury (25.00% vs. 21.43%, χ2=0.10, P=0.752), gastrointestinal reaction (28.57% vs. 35.71%, χ2=0.33, P=0.567), skin and mucosal injury (7.14% vs. 10.71%, χ2=0.35, P=0.553), nervous system disease (3.57% vs. 14.29%, χ2=2.25, P=0.134), endocrine reaction (3.57% vs. 10.71%, χ2=1.29, P=0.256), alopecia (14.29% vs. 17.86%, χ2=0.13, P=0.716) and fatigue (25.00% vs. 28.57%, χ2=0.27, P=0.605) between the control group and the test group. Conclusion:The combination of teriprizumab and bevacizumab can improve the short-term and medium-long-term efficacy of patients with MSI-H mCRC, which is safe and reliable.