This study is a multicenter, single-arm phase II trial, aiming to evaluate the efficacy and safety of neoadjuvant chemotherapy and immunotherapy combined with concurrent low-dose radiotherapy ± chemoradiotherapy as an adaptive neoadjuvant treatment for previously untreated resectable esophageal squamous cell carcinoma. Compared with neoadjuvant concurrent chemoradiotherapy, the pathological complete response (pCR) rate of neoadjuvant chemoradiotherapy is lower, and non-pCR has a relatively poorer prognosis than pCR. Therefore, how to further increase the pCR rate of neoadjuvant chemoradiotherapy under the premise of minimum toxicity is an important link to improve the efficacy of this treatment strategy. Low-dose radiotherapy provides an option for this strategy. Compared with traditional high-dose radiotherapy, low-dose radiotherapy is very safe, and the extremely low radiotherapy dose causes almost negligible damage to normal tissues. However, it can effectively reshape the immune microenvironment, converting cold tumors into hot tumors. On this basis, combined with immune checkpoint inhibitors, it can achieve effective immune responses in advanced tumors, bringing new hope for the treatment of advanced tumor patients. Low-dose radiotherapy can regulate the tumor immune microenvironment through multiple mechanisms and enhance the body's anti-tumor immune response, thus potentially further improving the efficacy of neoadjuvant chemoradiotherapy for esophageal squamous cell carcinoma.