This paper presents an auto-polarity thermo-electric energy harvesting circuit based on the reconfigurable thermoelectric generator (TEG) array. The auto-polarity function is achieved by simply altering the operating mode of the inverse current detector without adding extra power overhead and hardware cost. In addition, the proposed circuit consists of the TEG array and switches, removing the need for bulky inductor-based or switched-capacitor DC-DC converters. Hill-climbing algorithm is used for maximum power point tracking (MPPT). The operating frequency of the system is 0.2 Hz with overall dynamic power consumption of only 1.2mW. Over a wide range of temperature gradients, the static power is less than 0.1 μW with a peak efficiency of 99.6%.