Driving forces of grain growth during dynamic recrystallization of TA15 titanium alloy were analyzed theoretically and the equivalent negative driving forces concept for dynamic recrystallization grain growth was also proposed. Based on driving forces of dynamic recrystallization grain growth, a grain growth rate model and a grain size model describing grain size evolution of TA15 titanium alloy during dynamic recrystallization were established. Taking the experimental data of dynamic recrystallization grain size of TA15 titanium alloy as an example, the size model parameters were optimized by genetic algorithm (GA). The calculated results of grains size were in good agreement with the experimental values, whose average error was 7.4%