Abstract: To improve the power generation efficiency of the thermoelectric power generation device, a method for enhancing the performance of three-dimensional flat plate heat pipes was proposed. The effects of the two liquid filling rates on the thermal performance of the three-dimensional flat heat pipe were compared and evaluated by experiments, and the maximum output power and power generation efficiency of the thermoelectric power generation system under different temperature differences were explored. Results show that when the liquid filling rate is 27.4%, the three-dimensional flat heat pipe start-up process is staged start-up and the temperature stratification is significant. When the liquid filling rate is 31.7%, the three-dimensional flat heat pipe can be quickly activated at around 40 ℃, and the temperature distribution uniformity and consistency are good after start-up, which is conducive to the sustained, stable and efficient power generation of the thermoelectric power generation system. The maximum output power and power generation efficiency of the thermoelectric power generation system strengthened by three-dimensional flat plate heat pipes increase with the increase of the temperature difference, and the thermoelectric power generation efficiency can reach up to 3.99%.