A new two-stage thermoelectric couple (TE couple) is proposed in this paper. In order to overcome the disadvantages of 1-D heat transfer model mentioned in the previous research, 3-D finite element models are established based on the conventional thermoelectric couple and the two-stage thermoelectric couple separately, the temperature, convention and electric potential boundaries are defined and reasonable boundary conditions are set to simulate the models in ANSYS Workbench environment. Controlling variable method is used to study the influences of different input variables on the output performance of thermoelectric couples. Simulation results show that the load resistance influence the output voltage and current. The two-stage TE couple are better than the conventional one when load resistance is smaller than one critical value, but the maximum output power of the two-stage TE couple is always larger than the conventional TE couple.