Abstract: Zirconium alloys are the preferred material for nuclear fuel cladding. The hot working process has a crucial impact on the subsequent service performance of zirconium alloys. In order to investigate the effect of process parameters on the critical conditions of dynamic recrystallization in zirconium alloys, isothermal hot compression experiments were conducted for the Zr-Sn-Nb alloy using a Gleeble1500 testing machine at temperature of 680 ℃-880 ℃, and strain rate of 0.001 s^-1-5 s^-1. Based on the dynamic recrystallization critical kinetics theory and the true stress-true strain curve, the critical model of dynamic recrystallization was determined. The results show that the relationship between the critical strain ε_c and the peak strain ε_p is ε_c=0.359ε_p, and the predicted model of the dynamic recrystallization critical condition is ε_c=2.0675×10^-4 Z^0.1803. The established dynamic recrystallization critical prediction model shows a high similarity to the results of the hot compression experiments(R²≥0.9), indicating that the model can accurately predict the critical conditions of dynamic recrystallization in Zr-Sn-Nb alloy under thermal-mechanical coupling.