In recent years, the increasing prevalence of cancers constitutes a global public health crisis. Tumor incidence is closely related to individual living environment and diet is the most important part of it, especially for colorectal, gastric, pancreatic and breast cancer. Compared with normal cells, the energy metabolism of tumor cells is significantly changed since glucose uptake is increased, and anaerobic glycolysis has become the main energy resource for tumor cells. The ketogenic diet is a dietary mode that contains fat as the main food source. In this mode, ketone bodies become the main energy source for the body's cells. Therefore, in view of the unique metabolism of cancer cells, the ketogenic diet is considered to have a potential auxiliary anti⁃tumor effect which has been verified in many animal models, but its clinical application is still in exploration and there is still a lack of reliable evidence⁃based medicine guidelines. This article have specifically summarized clinical studies of the ketogenic diet in the field of malignant tumors, including clinical case reports, observational studies and clinical randomized controlled trials, and then discussed the current problems and challenges of applying the ketogenic diet in the clinical treatment of malignant tumors.