The contents and methods of prototype observation for channel improvement projects in mountainous rivers are deeply analyzed,and a set of prototype observation methods for channel improvement in mountainous rivers is proposed.Taking Minjiang River (Longxikou Junction to Yibin Hejiangmen) Waterway Improvement Project Phase I construction drawing design as a case study,the technical difficulties and key points of control survey,topographic survey and hydrographic survey are expounded.The measurement method and efficiency of prototype observation at three flow levels,namely,dry,medium and flood,are discussed,and the working period of measurement is reasonably arranged,which solves the problem that each item of hydrographic survey needs to be measured at the same flow level.The research results have reference significance for the prototype observation of channel improvement in mountainous rivers.