Obesity is not only an important risk factor for the occurrence, progression and metastasis of many types of cancer, but also may affect the tumor immune microenvironment to make the efficacy of tumor immunotherapy more significant, thus inhibiting the tumor, forming the "obesity paradox". Obesity can promote tumorigenesis by altering the levels of leptin and lipocalin, leading to the activation of abnormal signaling pathways and impaired immune cell function, and may also inhibit tumor progression by affecting the tumor immune microenvironment to make the efficacy of tumor immunotherapy more significant, but the specific mechanism is still unclear. This paper reviews the research progress of obesity through multiple mechanisms to remodel the tumor microenvironment, influence immune cell function, and the correlation between obesity and immunotherapy efficacy, aiming to provide a theoretical basis for optimizing tumor immunotherapy strategy.