In order to study the thermal runaway characteristics of lithium-ion battery modules in high temperature environment，based on the equation of energy conservation and the heat generation equation of side reactions，a three-dimensional numerical model of lithium-ion battery modules was established，and key physical processes such as temperature distribution，heat transfer，and heat generated by the side reactions within the battery modules were simulated，and the effect of parameters such as ambient temperature，heat transfer coefficient，initial temperature on the thermal runaway of lithium-ion battery modules was analyzed.The results showed that as the ambient temperature rised，more heat was generated inside the battery modules due to the accelerated rate of chemical reactions.When the ambient temperature reached 140 ℃，with heat transfer coefficients of 10 W/（m²·K），15 W/（m²·K） and 25 W/（m²·K），the heat of these reactions became quantitatively larger，and leaded to the occurrence of thermal runaway of the battery.Further，when the ambient temperature was 170 ℃，the heat transfer coefficients were 5 W/（m²·K） and 25 W/（m²·K），the thermal runaway of the battery module occured around 16 200 s and 4 600 s，respectively，and the peak temperature of thermal runaway was around 375 ℃.When the ambient temperature was 170 ℃，the initial temperature was 20 ℃ and 100 ℃，the thermal runaway of the battery modules occured around 9 280 s and 3 980 s，respectively，and the peak temperature of the thermal runaway was around 380 ℃.It showed that under the high temperature environment，the higher of the initial temperature and the higher of the heat transfer coefficient，the earlier thermal runaway occured，but both the initial temperature and the heat transfer coefficient had little effect on the peak temperature of the thermal runaway.