Abstract: Colorectal cancer is one of the most common malignancies in the world.Abnormal function of intestinal cells′ transmembrane signal transduction systems is associated with colorectal carcinogenesis,of which Ras/Raf/Mitogen-activated protein kinase(MAPK)cascade has been definitely and significantly involved.KRAS gene mutation leads the epidermal growth factor receptor(EGFR)′s initiation unnecessary for the activation of various genes in the downstream signal transduction pathways,which plays a major role in colorectal cancer′s genesis,progress therapy and prognosis.Therefore,testing KRAS gene status is essential in the clinical work,which demands for more precise of these processes.We sum up KRAS gene′s role in colorectal cancer and its mechanism,mutant incidence and testing methods.