Colorectal cancer is currently one of the most common malignant tumors in the world,and its incidence and mortality rates have gradually increased in recent years.As insidious symptoms characterize early colorectal cancer,most of the patients have already developed into late or advanced stages in the primary survey.For stage Ⅳ metastatic colorectal cancer(mCRC),surgery supplemented with chemotherapy or radiotherapy for mCRC patients has a low 5-year survival rate.With the development of immunology in recent years,PD-1/PD-L1 inhibitors have made breakthroughs in treating malignant tumors.They also have improved the therapeutic efficacy of some mCRC patients,especially those with microsatellite instability-high/mismatch repair deficient.The guidelines recommend this approach.However,patients with microsatellite stable/mismatch repair proficiency,which accounts for more than 90%,are poorly treated with PD-1/PD-L1 inhibitors.Fortunately,there are several clinical studies that reported that some of this type of mCRC can gain some benefit.In this review,we examined the anti-tumor mechanism of PD-1/PD-L1 inhibitors and the latest progress of PD-1/PD-L1 inhibitor's clinical application in patients of mCRC with different genotypes.We discussed the prospect of PD-1/PD-L1 inhibitor combination therapy to provide a reference to the benefit of this type of patients and provide information for optimizing the dosing regimen of PD-1/PD-L1 inhibitors in the treatment of mCRC.