Background and aim: Cancer is one of the deadliest diseases in the world, which is accompanied by abnormal growth, proliferation and sometimes proliferation of body cells. Based on research, 70 to 90 percent of common cancers are caused by environmental factors and are therefore potentially preventable. One of the most important prevention methods is microbiota, which includes microorganisms that live peacefully in close contact with the host. The purpose of this research is to investigate the role of intestinal microbiome in cancer. Material and Methods: In this research, we extracted the desired articles based on the keywords of cancer, tumor, microbiome, gut microbiome, Microbioa , normal flora and immune system from all databases such as ISI web of science, PubMed, Science direct, Google scholar, SID and Scopus.. A total of 150 articles were included in the screening study inclusion criteria and 35 articles were selected for use in the current review. Results: The studies of this research showed that optimal stimulation of gut microbiota can be a promising strategy to increase the effectiveness of cancer immunotherapy. On the other hand, besides the beneficial bacteria in the intestine, there are other bacteria that have an adverse effect on the tumor, and even their presence can be a favorable factor for the occurrence of a tumor. Conclusion: Identifying the intestinal microbiota profile for each patient may become a routine examination method in the future of medicine in cancer diagnosis. However, due to the large number of bacteria in the intestine, the discussion in this field needs more research and investigation.