A TEG composed of p-type higher manganese silicide and n-type magnesium silicide-stannide was evaluated by theoretical simulation based on finite element method and steady-state approximation. The geometry factors, heat flux, power output and the thermal electrical conversion efficiency of the TEG were calculated by applying the measured thermoelectric parameters of each leg into the simulation tool. Furthermore, the contact effect on the performance of the TEG was analyzed by separately introducing a contact layer between the thermoelectric legs and the metal layers having specific electrical and thermal conductivity. It was found that the different cross-sectional areas were required for the p-and n-type legs to achieve maximum module output or conversion efficiency. In ideal contact state, a promising efficiency of 8.29% can be obtained at a given temperature gradient. On the other hand, the performance of the TEG might be seriously deteriorated if the electrical or/and thermal resistance of the contact layer increased.