Colorectal cancer is the third most prevalent cancer in the world. Early screening and detection of tumours, active surgical radical treatment, postoperative adjuvant chemotherapy, targeted therapy, and immunotherapy are performed based on pathological staging and immunohistochemistry. Even with these measures, the 5-year survival rate of colorectal cancer is only 65%, and a considerable number of patients still experience tumour recurrence or even metastasis. The KRAS G12C mutation accounts for 3 to 4% of refractory colorectal cancer (advanced or metastatic colorectal cancer), and it was once believed that KRAS did not have a drug target until the emergence of KRAS G12C inhibitors provided targeted treatment for KRAS-mutated colorectal cancer. However, KRAS G12C inhibitors only produce moderate efficacy, and resistance occurs after a short remission. The mechanism of drug resistance in tumour cells is complex and diverse, and existing research has limited understanding of it. This review aims to elucidate the clinical trial progress of KRAS G12C inhibitors in refractory colorectal cancer, the research progress of drug resistance mechanisms, and the combined treatment strategies for drug resistance.