An experimental study on the measurement method of soil mercury was carried out in the typical section of Gulu geothermal field in Tibet. The experimental factors were discussed. A thermal reservoir of Gulu geothermal field was predicted and located with the existing geological understanding. The results showed that the mercury measurement can indicate the thermal anomaly under the Quaternary soil overburden in Gulu geothermal field. The experiment found that the sample collection horizon of Gulu geothermal field is the fine-grained soil at the lower part of layer A, the sampling depth is 20 cm, and the particle size is minus 200 mesh. When RA-915M mercury analyzer is used to measure the sample, the optimal mercury release temperature is 800 ℃, the gas carrying capacity is 0.2 L·s-1, the sample weight is controlled between 70～80 mg, and the test time is 2 minutes. Profile survey carried out at an appropriate scale can analyze the strong geochemical anomaly of extracted mercury. According to the abnormal characteristics, it can effectively indicate the concealed structure and the location of deep concealed thermal fluid channel. Therefore, method of soil mercury measurement is an effective prospecting and prediction method for exploring geothermal resources in covered areas.