Physical exercise is an important part of comprehensive cancer treatment and a great asset for tumor patients to promote recovery. Let’s first look at why exercise can fight cancer. Research shows that exercise is beneficial to cancer patients. First of all, exercise can enhance the body’s immune function. Exercise improves the body’s ability to produce white blood cells. Scientific research shows that exercise stimulates the secretion of certain hormones in the body, speeds up the production of white blood cells by bone marrow, increases the number of white blood cells, prolongs their survival time and increases the phagocytic ability of phagocytes. In this way, even if a small number of cancer cells appear in the body, they will soon be annihilated by the numerous white blood cells. In addition, the number and activity of immune cells in the body also rise with the increase of exercise, while the number of antibodies secreted by the mucous membrane of the respiratory tract and the digestive tract also increases significantly. This not only inhibits bacterial and viral infections, but also makes the specific and non-specific immunity in the human body to the killing ability of tumor cells are greatly improved, we must know that the immune system is the main weapon of the human body to fight against tumors. Only with this powerful weapon, we can achieve the final victory in the battle against cancer. Secondly, exercise can regulate the endocrine level, especially the sex hormone level. There is a significant correlation between estrogen levels and many gynecological tumors (e.g., ovarian cancer, breast cancer, endometrial cancer). The metabolism of estrogen in the body produces certain active products that contribute to the progression of these tumors. The production of these active products is related to the amount of fat in the body. The more fat there is, the more of this carcinogenic substance is produced. Regular exercise can greatly reduce the excess fat in the body, and it can make the secretion of estrogen in the body decrease, so it is beneficial to these tumor patients. Thirdly, exercise can make the body temperature rise, sweat a lot and accelerate blood circulation. It can prevent the generation of cancer cells and put cancer cells to “death”. It is measured that muscle heat production is high when exercising, and even rises above 4O degrees Celsius when exercising strenuously. Scientists have found that cancer cells are far less tolerant of heat than normal cells, and are easier to be killed by elevated body temperature. Along with the rise in body temperature, exercise also causes the body to sweat a lot, sweat can also be some carcinogenic substances such as strontium, lead, cymbals in the body in time out of the body. In addition, exercise also accelerates blood circulation, in which case the cancer cells that appear in the body or metastasize will be like small grains of sand in the rapids, unable to gain a firm foothold in one of the internal organs, grow and develop, and metastasize and spread. Fourthly, exercise makes the body inhale more oxygen. The amount of oxygen inhalation per minute is 4 to 7 liters when a person is quiet in general, while it can reach more than 100 liters when exercising. The increase of oxygen intake and the frequent exchange of gases can make some carcinogenic substances in the body to be discharged out of the body. Low-oxygen environment is very conducive to the growth and metastasis of tumors, while the oxygen inhaled by the human body during exercise, especially aerobic exercise, is about eight times of that in the quiet state, and the low-oxygen state in the body is corrected, which helps to inhibit the growth of cancer cells. Regular aerobic exercise can also effectively improve the activity of antioxidant enzymes, so as to continuously remove excessive free radicals in the body, reducing the incidence of cancer. Fifth, exercise can improve one’s mood and eliminate worries and troubles. There are reports that 30% of people suffering from cancer are too depressed and traumatized by their emotions. Exercise can make people feel good and forget their worries. Exercise, the brain will produce can cause the human body physical and mental happy substance “endorphin”, it can eliminate the sadness and worry, but also can lift the negative emotions on the immune system inhibition. In addition, to participate in collective sports, in the movement of mutual exchange of sports skills and feelings, so that the sportsman to obtain a clear sense of belonging to the team, reduce the sense of loneliness, so as to achieve the obvious psychological therapeutic effect. In conclusion, sports can not only enhance physical fitness, but also exercise the will, provide the material basis for cancer prevention, but also enhance the courage and confidence to overcome cancer.