A large signal equivalent circuit model for SiGe HBT is established based on the physical model of the transistor. The quasi saturation effect and the self-heating effect are taken into account in this equivalent circuit model. The model is composed of the intrinsic and the extrinsic parts, and has the features of clear physical meaning and simple topology. The model is embedded in the DEVEQ(Device Equations Developer) of PSPICE and simulated and analyzed by the PSPICE. The results conform to the theoretically analyzed conclusion and are in accordance with the published results in the literature.