Kaempferol induced apoptosis and S phase arrest effect bladder cancer cells by inhibiting the function of phosphorylated AKT (p-AKT), CyclinD1, CDK4, Bid, Mcl-1 and Bcl-xL and promoting p-BRCA1, p-ATM, p53, p21, p38, Bax and Bid expression. The gene discussed is CDK4; the disease is urinary bladder cancer.