Immunotherapy is a broad-spectrum anti-tumor treatment that primarily works by modulating the body's immune system to attack tumor cells.In recent years,immunotherapy has been widely applied in clinical practice,and has achieved remarkable effect in the treatment of different tumor species.However,immunotherapy can also induce various side effects,which can impact its use and leads to the early suspension of immunotherapy.There has been evidence that there is growing evidence that the host microbial environment may influence the efficacy of immune checkpoint inhibitors(ICIs)and is associated with the development of immune-related adverse events(irAEs).This article focuses on the relationship between immunotherapy-related side effects and microorganisms,with the aim of better understanding how the microbiome can be utilized to optimize immunotherapy strategies,mitigate adverse reactions,and improve patient quality of life.