Principles of medical oncology treatment include: choosing appropriate drug treatment plan, grasping the timing of treatment, balance and integrated treatment of tumor, organism and drugs, and comprehensive assessment of patient’s condition. 1. Choosing the appropriate plan: according to different types and stages of tumors, radiotherapy, targeted drugs, immune drugs, etc. are chosen to kill tumor cells as much as possible and slow down the progress of the disease. 2. Grasp the timing of treatment: the effect of treatment is inversely proportional to the load of tumor cells in the body, and internal medicine treatment should be carried out as early as possible when the load of tumor is low, and surgery can also be used to reduce the load of tumor. 3. Balance between tumor, body and drugs and comprehensive treatment: drugs have killing effect on tumor, but also hurt the immune function of the body, and the tumor has inhibitory effect on the immune function of the body. Medical oncology treatment should master the intensity and density of drugs, and at the same time, minimize the damage to the patient’s immune function. 4. Comprehensive assessment of patient’s condition: although medical oncology treatment can lead to radical treatment for some tumors, it is still palliative treatment for most tumors. The former should emphasize on dose intensity and consolidation of treatment, while the latter should weigh the possible efficacy and adverse effects, and pay more attention to the quality of life of patients. Medical oncology is a systemic therapy, which is an indispensable part of oncology treatment, and patients with malignant tumors should adopt individualized comprehensive treatment plan.