Based on classic rate-equation, by introducing the thermal effect, the rate-equations with temperature parameter correction were obtained. Then by using Simulink software tool, the nonlinear differential equation was simulated. Finally taking the parameter of a distributed feedback laser as an example, the transient solution of the rate equation under different temperature, bias points, and modulation signal was obtained, and based on which, the characters such as relaxation oscillation and frequency chirp were analyzed. The simulation results match the transient performance of this type of laser, and can provide reference for laser design and applicaion.