Objective: To investigate the molecular mechanism of Polyphyllin I (PPI) inhibits the proliferation of bladder cancer cells through intervening ADAR1 pathway. Methods: It has been confirmed whether PPI can modulate ADAR1, thereby inhibiting the proliferation of bladder cancer cells both in vivo and in vitro. Results: PPI inhibited the proliferation of bladder cancer cells in a dose-, time-, and concentration-dependent manner, significantly down-regulating the protein level of ADAR1 while increasing the levels of ZBP1 in vitro. Following the knockdown of the ZBP1 gene, PPI was unable to down-regulate the protein level of ADAR1; conversely, PPI could not increase the protein level of ZBP1 after the ADAR1 gene was overexpressed. In the animal experiment, PPI significantly inhibited the growth of tumors in Xenograft mice with bladder cancer cells, down-regulating the protein level of ADAR1 and up-regulating the levels of ZBP1, RIPK3, NLRP3, Caspase-1, and GSDMD. Conclusion: PPI may inhibit the proliferation of bladder cancer cells by suppressing the activity of ADAR1 and promoting the expression level of ZBP1 protein.