The issues of modeling the semiconductor laser with circuit elements have been addressed by several authors. Previously reported laser models are based upon rate equations and many relations between electron and photon. This needs the deep understanding of the clear physical meaning of all variables and the electrical and optical properties of the active region of a semiconductor laser diode. The relations and the formulas are very complex and the model's parameters are hard to get. In the previous models, node voltages are used as circuit variables. In practice the LD is powered by a constant or pulse current source. The node voltages are only measurable variables and decided by the input current for a ready-made LD. So taking the input current as the circuit variable is very simply and easy to understand and use. In this paper a circuit model of DHLD has been developed from rate equations and the well known models. Simulink module is built according to the rate equations. The input current is the only variable for the module. The transient response of the LD model is plotted. The simulating results such as transient and frequency responds agree well with the reported data.