Abstract: Tire Pressure Monitoring System (TPMS) is a necessary part for automobile safety. The battery-less TPMS on chip can overcome the disadvantages such as battery life and environmental pollution associated with batteries. This paper designs the main part of power recovery circuit for battery-less TPMS SoC, considering the distance of the wireless power transfer changes while the tires rolling. 125 kHz is chosen as the frequency of the battery-less system, and the design is based on ASMC's 0.35 μm BCD automotive electronic technology. Back simulation result shows that the 125 kHz AC input voltage, ranging from 0.8~15 V, can be converted to a 3 V DC source. Maximum output current of the power recovery circuit is 10 mA. The convention efficiency is also analyzed and optimized. The electromagnet interference and reliability of the TPMS are taken into consideration. The circuit can satisfy the TPMS working requirements in the practical environment.