Gastric cancer (GC),including cardia and noncardia gastric cancer, is responsible for over 480,000 new cases in 2020 and an estimated 370,000 deaths, making it the third most frequently diagnosed cancer and the third leading cause of cancer death in China. Majority of patients(63%) are presented with locally advanced gastric cancer (stage Ⅱ/Ⅲ) and the prognosis is poor. Previous studies have shown that patients with pathological complete response(pCR) following neoadjuvant therapy have longer survival. In 2019, Lancet Oncology published the FLOT4-AIO study which testified that perioperative chemotherapy with FLOT (5-FU/LV, oxaliplatin and docetaxel) regimen has improved pCR rate and prolonged progression free survival(PFS) and overall survival(OS) in patients with stage II/III gastric cancer. Moreover, PD-1 blockade such as nivolumab or pembrolizumab in combination with chemotherapy has shown higher objective response rate(ORR) as compared to chemotherapy alone in advanced gastric cancer. The nanoparticle albumin-bound paclitaxel has been recommended as the second-line chemotherapy for unresectable or recurrent gastric cancer based on the Chinese Society of Clinical Oncology(CSCO) guideline. When PD-1 antibody is applied, albumin-bound paclitaxel is considered as a better partner since no pretreatment of corticosteroids is needed. Thus, the investigators plan to conduct a phase II clinical trial to evaluate the efficacy and safety of toripalimab (PD-1 antibody) combined with the FLOAP (albumin-bound paclitaxel, oxaliplatin, fluorouracil and leucovorin) regimen as the perioperative treatment of cT2-4 and/or N+ GC. The primary end point is pCR rate. The secondary end points include disease free survival(DFS), OS, ORR, R0 resection rate, incidence of adverse events(AE).