Air-water heat exchangers are widely used in mine heat extraction owing to their advantages like simple structure and convenient installation and maintenance. Nevertheless, they are significantly influenced by air temperature; in low-temperature environments, they may even cause freezing at mine inlets, which in turn leads to the cracking of heat exchangers. Anti-freezing gravity heat pipes, a type of heat pipe technology capable of operating efficiently even in low-temperature conditions, offer an effective solution for mine heating in cold regions. This study investigates the heat transfer performance of gravity heat pipes under different charge amounts by analyzing experimental data of anti-freezing gravity heat pipes. By measuring data such as inlet and return water temperatures, mass flow rate, inlet and outlet air temperatures, and wind speed, the variation laws of key parameters like heat transfer rate, heat transfer coefficient, and thermal resistance under different charge amounts were calculated. The experimental results indicate that within the typical mine temperature range of 20 - 60 ℃, the heat transfer rate of the heat pipe increases monotonically with the rise in temperature. The optimal charge amount of the heat pipe corresponds to 43%-57% of the evaporator section volume (90-120 g), and the heat transfer rate is 121.21%-131.45% higher than that with the low charge amount of 30g. In this range, the heat transfer coefficient is 58.09-61.78 W/(m2·℃), and the thermal resistance is as low as 0.0806 - 0.0843 ℃/W. This research provides a basis for key parameters for the engineering application of gravity heat pipes in the field of mine heat extraction, and is expected to improve the efficiency and stability of mine heat extraction.