Aiming at the problem of single input voltage and narrow available power range in traditional TEG energy harvesting system, a DC-DC converter suitable for polarity reversal thermoelectric energy harvesting is proposed. The bipolar input buck-boost topology can adaptively collect bipolar input thermoelectric energy, and increase the energy storage buck-boost circuit, which effectively broadens the available power range under heavy load, ensures the stability of output voltage, and collects multiple buck-boost energy under light load, significantly improves the conversion efficiency of light load and ensures the endurance of the system. The maximum power tracking method adopts the open circuit voltage method with simple structure and high tracking efficiency. The 180 nm CMOS process simulation results show that the conversion efficiency of the proposed energy harvesting system under light and heavy load conditions is higher than 85 %, the maximum conversion efficiency is 9326% ( VTEG=500 mV, RS=210 Ω ), the maximum power tracking efficiency is 9952% ( VTEG =-600 mV ), the minimum operating input voltage of the circuit is ±25 mV, and the 18 V output voltage ripple under heavy load is less than 30 mV.