Abstract: Sanjiangyuan region is located in the hinterland of the qinghai-tibet plateau, with an average elevation of 3 500 to 4 800 m. The area is characterized by high cold, hypoxia and strong ultraviolet rays. The traditional river flow test method has certain limitations in the area, and with the continuous development of hydrology modernization, It is imperative to realize on-line monitoring of river flow. Taking the representative station of longwu river area of yellow river system in yellow river basin as an example, this paper analyzes the flow coefficient of the on-line flow measurement system of cable radar wave in tongren station, analyzes and determines the rationality of flow coefficient. It is a step forward to realize the on-line monitoring of river flow in Sanjiangyuan region.

Key words: Sanjiangyuan region, radar wave online flow measurement system, flow factor, comparison analysis