A thermoelectric generation system (TEGS) used in the practical industry of waste heat recovery consists of the fluidic heat sources, the external load circuitry, and many thermoelectric modules (TEMs) connected as a battery bank. In this paper, a system-level model is proposed to seamlessly integrate the complete fluid-thermal-electric-circuit multiphysics behaviors in a single circuit simulator using electrothermal analogy. First, a quasi one-dimension numerical model for the thermal fluids and their nonuniform temperature distribution as the boundary condition for TEMs is implemented in simulation program with integrated circuit emphasis (SPICE)-compatible environment. Second, the electric field calculation of the device-level model is upgraded to reflect the resistive behaviors of thermoelements, so that the electric connections among spatially distributed TEMs and the load circuitry can be freely combined in the simulation. Third, a hierarchical and TEM-object oriented strategy are developed to make the system modeling as well as the design scalable, flexible, and programmable. To validate the proposed system model, a TEGS, including eight TEMs is constructed. Through comparisons between simulation results and experimental data, the proposed model shows sufficient accuracy so that a straightforward cooptimization of the entire TEGS of large scale can be carried out.