Abstract: To investigate the geothermal characteristics in the Xisha Trough of the South China Sea, geothermal measurements were done in the area with a Ewing type heat probe, and thermal conductivities of the samples, collected from the heat flow sites, were measured with a thermal conductivity meter of TK04, and a heat flow profile with 7 heat flow stations was successfully obtained. The results show that the thermal conductivity of the top sediment ranges from 0.88 to 1.06 W/m·K, with an average of 0.96 W/m·K, and geothermal gradient ranges from 85 to 120℃/km, and heat flow ranges from 83 to 112 mW/m², with an average of 95 mW/m², which is according with the results of the geothermal measurement in the Xisha Trough area jointly conducted by the scientists of China and USA in 1980s. The accordance of two different measurements suggests that heat flow in the area is really quite high. The character of high heat flow is thought to be related with both regional and local factors, such as high heat flow background, the uplifted Moho surface, faulting activities, latest magmatism, and the undulation of the basement.