By selecting the fish habitats at the main stream of Dadu River 13.km below the dam of a hydropower station and in the upper tributary reaches 4.km above the confluence of Dadu River and tributary as studying objects, the habitat suitability evaluation was carried out from two aspects: the calculation of effective habitat area for fish and the simulation of river bottom connectivity of the tributary. The suitability indexes of two target fish, Schizothorax prenanti and Schizostomus distomus, in spawning period were analyzed and evaluated to obtain the suitability index of fish habitat suitability index and grade of fish habitat suitability index in the study reach. The habitat suitability index of fish in the main stream below the dam was 0.68, and the suitability grade was suitable. The habitat suitability index of fish in the 4.km river above the mouth of the tributary is 0.58, and the suitability grade is generally suitable.