From aspects of etiology, pathogenesis, treatment and commonly used prescriptions and herbs, this paper expounded traditional Chinese medicine (TCM) theories on cancer. Compound factors such as external evil invasion, diet damage and emotional disorders were causes of cancer in TCM theories. Clinically, TCM emphasized on expelling external evil as an important part in cancer treatment. However, characteristics of different diseases should be differentiated. Great attention should be paid to strengthening the body resistance. Generally speaking, ancient TCM doctors would used tonification herbs together with toxic herbs to benefitqi andyin as well as to promote blood circulation to remove blood stasis. Thus, the deficiency and excess were both considered. And the visible masses can be reduced from all-around and multi-level. This article suggested that TCM theories had great meaning of guidance in cancer treatment for current clinical oncologists.