To observe the inhibitory effect of the gnaphalium affine extracts on the formation of N-methylnitrosourea(MNU)-induced bladder tumor in rats，and to initially explore its mechanism.Methods:A total of 120 SD rats were divided randomly into 4 groups，high，medium and low concentration group，with 30 cases in each group.Bladder tumor was induced by intravesical instillation of MNU(1 mg/ times，once every 2 weeks,4 times)，inducing bladder tumors.The control group was given normal drinking water.High，medium and low doses groups were fed with high，medium and low concentration of the extract of gnaphalium affine extracts.All rats were killed at the 12th week，and their bladder tissue samples were taken to observe the difference in tumor formation rate.We took a specimen of its bladder tissue and observed its tumor formation rate.TUNEL method was used to detect the apoptosis of tumor cells.The expression of Survivin in rat bladder cancer tissues was detected by RT-PCR.Results:The tumor formation rate of bladder cancer in high，medium and low concentration groups was 60.11%(18/30)，75.86%(22/29) and 86.21%(25/29) respectively，while the rate of bladder cancer in the control group was 100%(28/28).In situ detection by TUNEL method，it was found that the gnaphalium affine extract can significantly promote the apoptosis of bladder cancer cells，which was related to the concentration; the expression of Survivin in rat bladder cancer tissues showed that the gnaphalium affine extract can significantly reduce the expression of survivin in rat bladder cancer tissues.Conclusion:The Gnaphalium affine extracts has a significant inhibitory effect on bladder cancer formation in rats.