Abstract: Pathogenesis theory of cancerous toxin is an innovative theory of traditional Chinese medicine oncology developed by the team, which has been widely used to guide the clinical differentiation and treatment for malignant tumors in recent years, and has achieved good clinical efficacy. Cancerous toxin is a specific pathogenic factor that causes malignant tumors and is the key pathogenesis for the development of malignant tumors. The team has been conducting research on the scientific connotation of pathogenesis of cancerous toxin for a long time. Through exploring the relationship between pathogenesis theory of cancerous toxin and tumor microenvironment as well as the correlation between pathogenesis of cancerous toxin and specific morbid substances in tumor microenvironment, the team comes up with that the scientific connotation of cancerous toxin is a specific morbid substance (affecting tumor genesis and development) in tumor microenvironment. In addition, the team also believes that inflammatory factors, lactic acid, angiogenic factors, immunosuppressive factors, and non-coding RNAs may be the biological basis for the pathogenesis of cancerous toxin. Applying modern oncology research progress, we interpret the scientific connotation of the pathogenesis of cancerous toxin, and provide scientific basis for further promotion of the theory of cancerous toxin and its clinical application.