The development of digital cities puts forward higher requirements for the basic data，and the demand for obtaining 3D spatial information of the surface is increasing day by day. AS-900HL multi-platform radar measurement system integrates a high-precision laser scanner and inertial navigation，which can be carried out on many platforms for data acquisition. It has the characteristics of high working efficiency，fast scanning，high density of measuring points，and various forms of results. This paper takes the topographic survey of the Baimalang to Yunfeng dam section of the Yalu River as an example to discuss the application of AS-900HL in river topographic survey. The terrain of this waterway section is highly undulating，and there is no direct contact measurement condition. Since the other side of the river is North Korea，there is no possibility of landing and setting up remote measurement equipment，nor is it possible to fly an unmanned aerial vehicle，which is a special river section that is very difficult to implement. Through exploration，route design，field collection，internal processing，and output，the feasibility of the system in waterway topographic survey is verified. This system is suitable for waterway topographic surveys，especially in difficult waterway sections. It can fill the gap that cannot be surveyed by conventional survey technology. To go further，it has a positive effect on the construction of the digital channels and digital cities.