In this paper, to simulate the temperature-dependent output characteristics of quantum cascade lasers (QCLs) we present a new circuit-level model. The equivalent circuit model of the laser by employing a number of standard quantum mechanical approaches such as the carrier coherent transport, a simplified four-level carrier scattering rates and heat transfer equation is developed. The presented equivalent circuit can be divided in three interactive circuits including: the biasing circuit that accounts for the coherent transport using sequential resonant tunneling to adopt the current-voltage relationship in the device the intrinsic QCL circuit that includes the rate equations describing the carrier dynamics inside the device active region levels the thermal circuit, which incorporates the heat dissipation. Using the presented model, the thermal characteristics of a QCL under the steady and dynamic conditions are investigated. The excellent agreement of the experimental data with the simulated temperature-dependent light output-current characteristics confirms the validity of the model.