Background: Microsatellite instability (MSI) is widely acknowledged as a reliable clinical biomarker linked to survival advantage due to its immunogenicity. This study aimed to synthesize information on the prevalence and prognosis of cancers with high MSI (MSI-H) or deficient mismatch repair (dMMR) to understand the disease burden and clinical value in Chinese cancer patients. Methods: A comprehensive search of English databases (PubMed, Web of Science, Embase, and Cochrane) and Chinese databases (CNKI and WanFang) was conducted to identify studies published through September 5, 2022 that examined the prevalence and prognosis of tumors with MSI-H/dMMR among Chinese cancer patients. Meta-analysis was conducted to evaluate the pooled prevalences of MSI-H/dMMR across various tumor types and stages. Results: A total of 106 studies reported the MSI-H/dMMR prevalence, of which 53 studies also reported clinical outcomes of cancers by MSI-H/dMMR in Chinese cancer patients. MSI-H/dMMR pooled prevalence (95% confidence interval; number of studies included) was estimated for endometrial: 24.7% (17.7%-32.4%; N=15), liver: 19.0% (6.4%-36.0%; N=3), colorectal: 13.6% (10.8%-16.7%; N=57), gastric: 10.1% (5.5%-16.0%; N=14), ovarian: 8.8% (1.8%-19.8%; N=4), urothelial: 6.8% (0.2%-23.3%; N=2), and lung cancer: 0.7% (0%-7.6%; N=3). We observed a general pattern of lower MSI-H/dMMR prevalence in advanced-stage compared with early-stage cancers. Furthermore, the presence of MSI-H/dMMR with a positive prognosis was predominantly observed in early-stage cancers rather than advanced-stage cancers, particularly among patients who did not receive immunotherapy. Conclusions: In this comprehensive review of cancer patients in China, the most frequently studied cancer types for MSI-H/dMMR were endometrial, colorectal, and gastric cancers. These cancer types also exhibited the highest prevalence of MSI-H/dMMR, with a lower prevalence observed in later stages compared to early stages. Overall, MSI-H/dMMR was more commonly linked with a favorable prognosis in early-stage cancers rather than advanced-stage cancers.