Objective:To observe phenomenon of Molt-4 cell apoptosis induced by TNF-αand expression of cyclin B1, and investigate the receptor-mediated apoptosis mechanism. Methods:Exponentially growing human leukemia cell lines(Molt-4) were treated with TNF-α. Method of API was used to detect the apoptosis, and method of western blot was applied to illustrate expression of cyclin B1. Results:Molt-4 cells which were treated by TNF-α went to apoptosis. Apoptosis was in G1-phase, and the expression of cyclin B1 was observed in G1-phase. Conclusion:Cell apoptosis induced by TNF-α was closely related to cell cycle and presented cell-cycle-specificity. The expression of cyclin B1 increased in G1-phase, which may be related to cell apoptosis in G1.