Abstract: In order to improve the battery life of wireless sensor nodes, a thermoelectric energy harvesting reconfigurable DC-DC converter for battery powered wireless sensor nodes is proposed. The converter is divided into three modes: energy storage, light load and superposition, and realizes the reconstruction of different input power and modes to adapt to the load hopping. The newly proposed superposition mode can collect thermoelectric energy under heavy load and achieve full time energy collection in combination with light load. To solve the problem of large output ripple of traditional DC-DC converter, this paper designs a mode switching circuit and a dead-time control circuit to suppress output voltage ripple. In order to maximize the output power, the maximum power tracking circuit is designed to track the internal resistance of the input source. At the same time, the conventional discontinuous on-mode (DCM) is abandoned and the critical on-mode (CRM) is adopted to reduce the conduction loss and improve the peak conversion efficiency at higher input power. The 180 nm CMOS process simulation shows that the input power range is 500 µW~8 mW, and the maximum end-to-end peak conversion efficiency can reach 87.32% (V_TEG=400 mV,R_TEG=5 Ω) in light load mode. The power of the thermoelectric generator is extracted preferently when the power is supplied in superposition mode. Up to 66% of battery power can be saved under heavy loads, and the 1.1 V output voltage ripple is less than 20 mV under heavy loads, and the output power range is 50 µW to 10 mW.