Firstly, based on the river health evaluation theory and starting from the integrity of the river system, the river health evaluation index system is selected. Secondly, the index systems of river health assessment including river morphology, hydrological and environmental characteristics, habitat elements and human activity characteristics are determined. Thirdly, set-pair (SPA) evaluation theory and extension were dealt with, a set-pair analysis-extension coupling model is constructed. Finally, taking Huangchuan Rive as an example, the ecological health evaluation on the river channel is carried out by using set-pair analysis-extension coupling model. The results of the comprehensive evaluation using the set-pair analysis-extension coupling method is obtained through calculation. It is proved by practice that the method of river health evaluation using the coupling model of set-pair analysis and extension theory could make full use of the data transformation and extension calculation, which shows the superiority in calculating correlation degree, and could reflect the determination and uncertainty of practical problems. It is possible to comprehensively consider all relevant factors. The paper provides a new idea for solving the relevant problems and obtains more accurate conclusion.