This paper presents an improved model of thermoelectric power generation, taking into consideration the effect of air heat transfer in a closed cavity between the thermoelectric couples. We have used the ANSYS software, under the condition of different numbers of thermoelectric couples and different models, to simulate numerically and analyze the temperature field and, the voltage field of thermoelectric power generation. Results show that the energy conversion efficiency of 127 pairs of thermoelectric couples increases rapidly as the temperature gradient between the hot and cold ends increases as compared with 1 pair of thermoelectric units; it is enhanced from 0.39% to 5.16% at an average of 3.02% while the temperature gradient varies from 20℃ to 220℃. The output voltage of the chip, power, and energy conversion efficiency would increase as the cross-sectional area increases while the cold junction temperature stays at 305℃, and the cold arm galvanic greater the temperature difference across the greater the increase rate, and thermoelectric power generation chip resistance, along with the cross-sectional area of the galvanic arm decreases. The output power can be up to 28.9W as the temperature difference is 220℃.