Abstract: About 1/3 of patients with colorectal cancer have a genetic background. Familial colorectal cancer type X refers to colorectal cancer clinically in line with Amsterdam criteria Ⅱ, but genetic testing of which does not show microsatellite instability or DNA mismatch repair gene mutations. Its tumor cell gene is microsatellite stable. Attention should be paid to the differen-tiation from Lynch syndrome. Familial colorectal cancer type X is highly heterogeneous, without unclear etiology so far. It is recommended to refer to sporadic colorectal cancer for diagnosis, treatment, follow-up and prevention. The authors introduce the diagnosis and treatment of a case of familial colorectal cancer type X, in order to provide references for clinical diagnosis of this disease.