• Have fully understood and voluntarily sign the ICF for this study;

• Age of 18-70 years (inclusive), male or female;

• Esophageal squamous cell carcinoma confirmed histologically or cytologically

• Second-line patients with disease progression after only first-line standard therapy（Standard treatment: chemotherapy with platinum plus fluorouracil or taxane combined with immunosuppressive regimen .Progression during adjuvant/neoadjuvant therapy or within 6 months of the last dose is considered a first-line standard treatment failure）

• At least one measurable lesion according to RECIST 1.1;

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) score of 0-1;

• Expected survival is more than 3 months

• Adequate organ function, defined as:

• Absolute Neutrophil count (ANC) ≥ 1.5 × 10\^9/L; Platelet count (PLT) ≥ 75× 10\^9/L; Hemoglobin (Hb) ≥ 90 g/L; Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × upper limit of normal (ULN) (≤ 5.0 × ULN for patients with liver metastases); Serum total bilirubin (TBIL) ≤ 1.5 × ULN; Serum creatinine ≤ 1.5 × ULN and Creatinine clearance (CCr)≥60mL/min; Prothrombin time (PT)、activated partial thromboplastin time (APTT)、international normalized ratio(INR)≤1.5 × ULN;

• Male and female patients of childbearing age must agree to take effective contraceptive measures during treatment and within 6 months after the last dose of treatment.