Abstract: Small cell lung cancer (SCLC) is one of the most refractory tumors. Approximately two-thirds of patients have been reported to have extensive-stage small cell lung cancer (ES-SCLC) when diognosed, with a survival time of less than one year. With the successful application of immune checkpoint inhibitors to a variety of solid tumors, several clinical studies have been conducted on immunotherapy for ES-SCLC. However, this present higher requirements and challenges for application of effective strategies in different disease stages. This paper reviews the completed immune-related clinical research in naïve and treated ES-SCLC patients in recent years. In this article, PD-1 inhibitors, PD-L1 inhibitors, CTLA-4 inhibitors, immune checkpoint inhibitor monotherapy and combined immunotherapy, and biomarkers for predicting treatment efficacy have been explored. This article summarizes the best treatment model, deeply considers future research directions, and attempts to improve the efficacy and survival of patients with ES-SCLC.