Small-Cell Lung Cancer (SCLC) accounts for 10% to 15% of new lung cancers and is a highly aggressive neuroendocrine tumor. In the past 30 years, the treatment of SCLC has made very limited progress, and basically made breakthroughs in radiotherapy and chemotherapy. With the advent of the immune era, immunotherapy has achieved initial results in the treatment of SCLC. Approximately one-third of patients with small cell lung cancer are in limited-stage (LS-SCLC) disease at first diagnosis. Except for a very small number of patients with T1-2N0 who can be treated with surgery or stereotactic radiation therapy (SBRT), the standard treatment for the rest of the patients with LS-SCLC is concurrent chemoradiotherapy. The ORR of platinum-combined etoposide regimen combined with thoracic radiotherapy in LS-SCLC can reach 70% to 90%, and the median OS is 16-24 months, which significantly improves the survival of patients. Although many measures have been taken in the treatment of LS-SCLC, only 20% of LS-SCLC can be cured, and most patients have relapse and metastasis after treatment. This study is a single arm phase II preliminary pilot study, aim to assess the efficacy and safety of durvalumab combined with EP prior to CRT and followed by durvalumab consolidation therapy for LS-SCLC.