A gravitational flat-plate heat pipe is designed and fabricated in this paper to serve as a heat spreader to diffuse the local heat source to the hot side of the thermoelectric power module. Based on this, an experimental test for the thermoelectric power generation system is conducted to study the influences of the heat spreader on the temperature uniformity and power generation performance when exposing to a local heat source. In addition, the effects of the heating power, inclination angle, and local heat source size on the power generation performance of the thermoelectric power module using a flat-plate heat pipe as a heat spreader are examined and compared with that using a metal plate. The results indicate that the gravitational flat-plate heat pipe has considerable advantages over the metal plate in the temperature uniformity. The superiority of temperature uniformity in the improvement of power generation performance for the thermoelectric power system using a heat pipe is demonstrated. Particularly, the heat pipe shows good adaptability to placement mode and the local heat source size, which is beneficial to the application in the thermoelectric power generation. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.