Abstract: Under normal circumstances, the gut microbiota and the proportion of symbiotic bacteria, probiotics, and pathogens remain relatively stable, but dysbiosis in the gut can change not only the physiological environment of the intestine but also the physiological state of some distant tissues and organs.This condition can even lead to tumor development.Gut-brain axis is a pathwaythrough which gut microbiota can influence tumor growth and is associated with other pathways, such as immune, metabolic, neuroendocrine, and vagal neural pathways.This paper reports the relationship between tumor growth and microbial groups in the gut andthe mechanisms of gut dysbiosis inducing a chronic stress state via the gut–brain axis, which affects tumor development.This paperalso presents the role of gut microbiota in tumor treatment.