With the discovery of magnetoreceptor mechanisms in animals, it materialized the novel applications of controlling cell and animal behaviors using magnetic fields. T cells have shown to be sensitive to magnetic fields. Here, we reported that exposure to moderate SMFs (static magnetic fields) led to increased granule and cytokine secretion as well as ATP production and mitochondrial respiration from CD8+ T cells. These effects were inhibited by knocking down the Uqcrb and Ndufs6 genes of mitochondrial respiratory chain, whose transcriptions were regulated by candidate magnetoreceptor genes Isca1 and Cry1/Cry2. SMF exposure also promoted CD8+ T cell granule and cytokine secretion and repressed tumor growth in vivo. SMFs enhanced CD8+ T cell cytotoxicity, and the adoptive transfer into tumor-bearing mice resulted in enhanced antitumor effects. Collectively, our study suggests that moderate SMFs enhance CD8+ T cell cytotoxicity by promoting mitochondrial respiration and promoted the antitumor function of CD8+ T cells.