For the problem that existing numerical simulation methods are unable to accurately reflect the probabilistic temperature variations caused by thermal runaway in lithium batteries， s a modeling method for the thermal runaway propagation of lithium battery modules based on probability function triggering is proposed. This method calculates the triggering probability of thermal runaway in each temperature range by statistical analysis of the temperature range and distribution of actual thermal runaway events in lithium batteries. Based on the proposed probabilistic trigger simulator， the simulation process is probabilistically triggered. The effectiveness of the method is verified by comparing simulation results with experimental data， showcasing a high degree of correlation. Then， the thermal spread paths and their probabilities under different triggering conditions of the probability function are analyzed， revealing multiple potential routes for thermal runaway， including the jump thermal runaway event. The sequential thermal runaway path is identified as the most probable， while the jump phenomenon is deemed least likely. The proposal of this method further improves the consistency between numerical simulation and actual process of thermal runaway in lithium batteries， providing an effective research tool and analysis method for studying the probability of thermal runaway propagation in lithium battery modules.