The mechanism of tumorigenesis in the brain is very complex and still has not been fully understood. However, according to the current situation, the root cause of tumor in the brain is the mutation of normal cells into tumor cells due to genetic mutation, and their growth is uncontrolled, thus producing tumor in the brain. The factors that cause the mutation of normal cells in the brain may include the following: a. Environmental pollution, as environmental pollution is becoming more and more serious, various toxic elements may enter the body and cause the mutation of genes to form tumors. Second, ionizing radiation, the use of a large number of electrical appliances, especially cell phones, will produce a large amount of radiation, which may lead to mutation of intracranial cells and cause intracranial tumors. The decrease of immunity of the body, including long-term staying up late, mental stress, fatigue and autoimmune diseases, will lead to the decrease of immunity of the body, which will make tumor cells escape from immunity and lead to the malignant growth of tumor and intracerebral tumor.