In this paper,an equivalent circuit thermal model is derived based on quantum cascaded laser′s (QCL) two-level rate equation by analyzing the gai n characteristic depend on the temperature in active region.The model enables the analysis of the thermal characteristics of intermediate infrared qua ntum cascaded laser (QCL) using general circuit analysis software,which overcomes the shortcomings of complex pr ocess a nd long simulation time of numerical analysis method.The modeling and simulation are implemented in PSPICE ,and the results are in agreement with the reported theoretical and experimental data.That proves the pr acticality and accuracy of the model.