Purpose: Based on the suggestion of REGONIVO study, we reviewed the data of 26 MSS mCRC patients to elaborate the efficacy and safety of fruquintinib (a VEGFR inhibitor) plus PD-1 inhibitor and explore the potential predictors for survival in 3+ line microsatellite stable (MSS) metastatic colorectal cancer (mCRC) patients.Patients and methods: This retrospective study enrolled 26 MSS mCRC patients who progressed after at least 2 lines of systematic chemotherapy but didn’t receive PD-1 inhibitors. Fruquintinib of 3mg was administered once daily with 21 days on/7 days off plus PD-1 inhibitor 200mg every 3 weeks until intolerable toxicity or disease progression. Results: Median overall survival (mOS) was 6.1m (ranged 1.8m-NR 95%CI: 2.60-9.60); median progression free survival (mPFS) was 2.3m (ranged 1.5m-NR 95%CI: 0.93-3.67). There was one complete response (CR) and no partial response (PR). Stable disease was observed in 11 patients (42%) and progression disease (PD) was observed in 14 patients (54%). The object response rate (ORR) was 4% (1/26) and disease control rate (DCR) was 46 %( 12/26). Grade ≥3 AEs were observed in 5 patients (19.2%). Grade 5 AEs (immune related encephalitis and cardiotoxicity) were observed in 2 patients. Additionally, there was a significant correlation between NLR < 3.06 and longer survival (P=0.000) for MSS mCRC patients treated with fruquintinib plus PD-1 inhibitor. Conclusions: Fruquintinib plus PD-1 inhibitor may be a choice for 3+ line MSS mCRC patients，especially with pretreatment NLR<3.06.