Objective · To investigate the effects of soluble CD40 Ligand (sCD40L) on the proliferation, apoptosis of Kasumi-1 cells in vitro and its mechanism. Methods · Different densities of sCD40L were applied to Kasumi-1 cells and the MTT assay was used to observe the inhibiting effects of sCD40L on the cell proliferation at 24, 48 and 72 h to screen the optimum concentration of sCD40L and intervention time. After Kasumi-1 cells were treated with the optimum concentration of sCD40L and time, the flow cytometry (FCM) was adopted to test the apoptosis and cell cycle of Kasumi-1 cells, Western blotting was used to measure the expression of Cytc, Bax, Bid and Bcl-2, ELISA was used to test the expression of IL-17 in the culture supernatants. Results · The optimum sCD40L experimental concentration and intervention time was 4 μg/mL and 48 h. After Kasumi-1 cells were disposed by sCD40L, the cell proliferation was inhibited and the apoptosis was increased significantly. SCD40L could change Kasumi-1 cell cycle distribution which showed increasing the proportion of cells in G1 phase and reducing the proportion of cells S phase. The expression level of proapoptotic factor Bax, Bid, Cytc of Kasumi-1 cell and IL-17 in cell culture supernatant were decreased and anti-apoptotic factor Bcl-2 was increased. Conclusion · SCD40L can significantly suppress Kasumi-1 cells proliferation and induce Kasumi-1 cells apoptosis. The mechanism maybe involve mitochondrial pathways and up-regulation of IL-17 level.