Background: Immune checkpoint inhibitors have been approved for first- or third-line treatment of metastatic gastric cancer. However, pembrolizumab alone did not improve overall survival compared to second-line chemotherapy in the KEYNOTE-061 study. We aimed to explore the safety and efficacy of a three-drug regimen by carrying out a clinical study of PD-1 inhibitor combined with albumin paclitaxel and apatinib (VEGFR inhibitor) in the second-line treatment for patients with metastatic gastric cancer(mGC). Methods: This study was a single-center, single-arm phase II clinical study. patients harboring microsatellite stable (MSS) who had previously failed in first-line treatment were enrolled. The enrolled patients were given PD-1 inhibitor (PD-1 inhibitor selected according to the patients’ requirements) in combination with albumin paclitaxel (125 mg/m² IV, D1, 8 days or 250 mg/m² IV, D1, 250 mg and apatinib 250 or 500 mg orally for D1-21 days, every 3 weeks as a cycle). The primary endpoints were progression-free survival (PFS) and objective response rate (ORR), while the secondary endpoints were overall survival (OS) and safety (AEs), disease control rate (DCR). Results: From July 11, 2019 to December 1, 2021, a total of 23 patients were enrolled, of whom 10 had negative PD-L1 expression, 1 had PD-L1 > 70% expression, and 4 had positive PD-L1 expression. Preliminary results showed 8 cases had partial response (PR), 10 cases had stable disease (SD), and 5 cases of progression disease (PD). ORR was 34.8% and DCR was 78.3%. The median PFS was 5.04 m, and the median OS was not reached. The main adverse reactions of grade 1 to 2 were bone marrow suppression (42.8%), hand-foot reaction (21.4%), hypertension (21.4%), gastrointestinal bleeding (13.0%), hypothyroidism (8.7%), and liver function damage (8.7%). No grade 3-4 adverse reactions were reported. Conclusions: PD-1 inhibitor combined with albumin paclitaxel and apatinib in the second-line treatment of metastatic gastric cancer showed certain efficacy and safety. At present, this study is ongoing to further confirm the anti-tumor effect and survival benefit of this regimen. Clinical trial information: NCT04182724.