Abstract: Under the guidance of the theory of cancerous toxin pathogenesis, it is proposed that the common pathogenesis of colorectal precancerous lesion is damp-heat toxin accumulation and deficiency of spleen qi. Damp-heat toxin is induced by deficiency of spleen, retained in zang-fu organs and then transformed into cancerous toxin. Deficiency of spleen is the fundamental pathogenesis of colorectal pre-cancer lesion while damp-heat toxin accumulation is the development condition. The endogenous cancerous toxin is the key to cancerization. Combined with endoscopic pathological grading, the evolution of pre-colorectal lesion can be divided into cancerous toxin-free period and cancerous toxin period according to whether there is endogenous cancerous toxin or not. The process of disease onset induced by cancerous toxin is the process of colorectal precancerous lesion transforming into colorectal cancer. Therefore, according to the pathogenesis of colorectal precancerous lesion either in cancerous toxin-free period and cancerous toxin period, corresponding treatment methods should be applied to remove the source of cancerous toxin or endogenous cancerous toxin, which can achieve the purpose of inhibiting cancerization and reversing the formation of cancer.