To fully utilize automobile exhaust waste heat, a thermoelectric generator can be used to recover waste heat energy. In this study, an engine exhaust thermoelectric generation model based on a smooth plate-type exhaust heat exchanger is established, and the thermoelectric performance is quantified using Fortran. To achieve the maximal net power output of the thermoelectric generator, the different series circuit layouts of the thermoelectric module were compared, and the structural optimization of the exhaust heat exchanger was performed. The results show that there are optimal values for the total length, width, and height scale of the exchanger for both the full-and two-stage series circuit types. At the exhaust temperature of 500 °C and mass flow rate of 30 g s-1, the optimal exchanger heights of the full-and two-stage series types are both 4 mm, and the optimal number of thermoelectric units Ny,opt in the y direction is 68 pairs. The optimal number of thermoelectric units Nx,opt in the x-direction is 44 pairs for the full series type and 54 pairs for the two-stage series type. When the corresponding optimal scales are utilized, the two-stage series type increases by 11.39 % compared with the full-series type.