Background: Although anti-PD-1 antibody in combination with chemotherapy has shown promising antitumor activity in advanced gastric or gastroesophageal junction adenocarcinoma (GC/GEJC), the evidence of conversion therapy for initially unresectable GC/GEJC is limited. Camrelizumab combined chemotherapy as conversion therapy for unresectable GC/GEJC was a prospective, single-arm, phase 2 study we conducted. Here, we updated the results of efficacy and safety of this study. Methods: Patients with HER-2 negative and PD-L1+ (CPS≥1) or MSI-H/dMMR, or EBV (+) unresectable gastric cancer were enrolled. Eligible patients must meet one of the following criteria: 1) peritoneal metastasis (CY1P0 or P1a, P1b or PCI < = 10); 2) liver metastasis (H1), < 3 metastatic sites; 3) para-aortic lymph node metastasis. For patients with lymph node metastasis or liver metastasis, they received 6 cycles of camrelizumab (200mg ivgtt on day1, q3w) plus SOX (Oxaliplatin, 130mg/m² ivgtt, d1, q3w, S-1 40/50/60 mg based on BSA, po, bid, d1-14, q3w) as conversion therapy. For patients with peritoneal metastasis, they received 6 cycles of camrelizumab (200mg ivgtt on day1, q3w) plus IP (Paclitaxel, 50mg/m², ivgtt, d1, d8, q3w. Paclitaxel, 20mg/m², intraperitoneal administration, d1, d8, q3w. S-1 40/50/60 mg based on BSA, po, bid, d1-14, q3w) as conversion therapy. Then patients without disease progression evaluated by imaging underwent gastrectomy of D2 lymph node dissection. The primary endpoint was R0 resection rate and 2 years survival rate, the secondary endpoints were objective response rate (ORR), pathological complete response (pCR) rate and overall survival. Results: Between December 30, 2020 and January 5, 2022, 31 patients were enrolled. 19 patients received SOX plus camrelizumab, 12 patients received IP plus camrelizumab. Unfortunately, 7 of them were confirmed PD by imaging. In addition, two patients refused gastrectomy and withdrew from the study. 12 patients underwent gastrectomy and 8 patients are in the process of conversion therapy. Among the 12 patients were evaluable, 9 of them gained R0 resection (75%), 1 patient (8.3%) achieved pCR and 2 patient (16.6%) reached TRG1. The most common grade 3 adverse events (AEs) were neutropenia (27.6%). No serious AEs resulted in termination of treatment or death. Conclusions: Camrelizumab combined with chemotherapy was an effective and safe conversion therapy strategy for patients with unresectable GC/GEJC. Furthermore, the analysis of biomarkers with clinical benefits is undergoing. Clinical trial information: NCT04694183.