This is a randomized, double-blind, placebo-controlled, multicenter study. The main purpose of the study is to evaluate the clinical efficacy and safety of nimotuzumab combined with trifluridine/tipiracil in third-line and beyond for the treatment of metastatic colorectal cancer (mCRC). This study planned to be divided into two parts: Part A and Part B. Part A (safety run-in) with a 3 + 3 study design, which primary endpoint is safety; Part B (main study) with a prospective, randomized, double-blind, placebo-controlled design, which primary endpoint is overall survival (OS).