Esophageal cancer is one of the most common malignancies in China, and esophageal squamous cell carcinoma (ESCC) is the predominant histological type. Surgical resection is still a standard therapeutic approach for patients with resectable ESCC, but the prognosis is still disappointing. Although neoadjuvant chemoradiotherapy plus surgery is currently recommended for patients with locally advanced ESCC, it is still an infrequently used procedure in China. The efficacy of adjuvant therapy on ESCC is still controversial. Recently, the CheckMate 577 trial showed that adjuvant nivolumab therapy could improve DFS for patients with residual disease after neoadjuvant chemoradiotherapy plus surgery. However, no optimal postoperative adjuvant therapy was recommended for patients with ESCC received upfront surgery. We designed a prospective randomized controlled tial to study whether immunotherapy could be used with chemotherapy after surgery to improve overall survival in these patients. The primary endpoint of the study is disease free survival, with secondary endpoints of overall survival, safety and toxicity, and quality of life.