Abstract: Lung cancer is the leading cause of cancer-related deaths worldwide, and non-small cell lung cancer (NSCLC) is the most common type. Because more than one-third of NSCLC patients are diagnosed at stage Ⅲ, most of these tumors are unresectable. Chemoradiotherapy (CRT) is the standard treatment for unresectable stage Ⅲ NSCLC; however, its curative efficacy is poor. Compared with simple CRT, the survival rate of patients with unresectable stage Ⅲ NSCLC following consolidated immunotherapy after CRT has significantly improved owing to the emergence of immune checkpoint inhibitors. However, a subset of patients do not benefit from consolidated immunotherapy. Based on the effectiveness of induction immunotherapy in resectable stage Ⅲ NSCLC, studies have been conducted to extend its application in unresectable stage Ⅲ NSCLC. This article reviews the mechanism of action, recent advancements in clinical research, and cycle of induction immunotherapy before radiotherapy in unresectable stage Ⅲ NSCLC to provide a reference for clinical treatment of unresectable stage Ⅲ NSCLC.