Abstract: Groundwater- surface water interactions in the middle reach of Heihe River were investigated by measuring the streambed and stream surface temperatures through fiber-optic distributed temperature sensing (DTS). The DTS system used in this study has a temperature resolution of 0.01℃, sampling interval of 0.25 m and temporal interval of 4 minutes. By continuously monitoring the streambed and stream surface temperatures along the river channel through a fiber-optic cable, the 550m long river segment was identified as a groundwater discharge zone. Based on the comparison of observed temperature variations in the atmosphere, streambed and stream surface, the distribution and variation pattern of temperature anomalies were easily identified, thus providing an effective means of studying and revealing the groundwater-surface water exchange along a stream channel.