GLOBOCAN 2020 reported that the global incidence of esophageal cancer climbed to 604,100, accounting for 3.1% of all tumor sites and ranking 7th out of 36 cancers. In addition, about 544,076 new esophageal cancer deaths, which accounted for 5.5% of all study centers and ranked 6th among 36 cancers. Esophageal squamous cell carcinoma (ESCC) is the most common pathological type of esophageal cancer in China, and accounts for about 90% of cases. Immunotherapy has become the main treatment for second-line and later esophageal cancer patients, but because of the single target, limited mediated signaling pathway, and high drug resistance rate, single-target blocking has limited efficacy. Cadonilimab is a novel humanized bispecific antibody targeted by programmed death receptor 1（PD-1）/cytotoxic T-lymphocyte antigen 4 (CTLA-4)，which can simultaneously block the two immune checkpoint pathways of PD-1 and CTLA-4, indirectly "liberating" immune cells, and improving immune efficacy. Anlotinib inhibits tumor angiogenesis by fully acting on the VEGFR/PDGFR/FGFR pathway, while remodeling tumor microenvironment, increasing T cell activity and infiltration, and synergizing immunotherapy. In addition, the control of local tumors or oligometastases by radiotherapy combined with systemic therapy such as immunotherapy has become an important research direction for metastatic esophageal cancer. This study will explore the efficacy and safety of cadonilimab combined with anlotinib sequential radiotherapy for the treatment of recurrent or metastatic esophageal squamous cell carcinoma (ESCC) at second or later line.