SIMHYD model has simple structure and few parameters, so it is widely used in monthly and daily scale watershed runoff simulation. Due to the lack of watershed confluence part in the model structure, SIMHYD model cannot meet the needs of hour-scale flood prediction and simulation. For this reason, SIMHYD model was studied in this paper. In view of the shortcomings of the model structure, four different confluence scenarios were designed and compared on the basis of SIMHYD model: (1) No confluence was considered（original SIMHYD model）; (2) Only increase channel confluence; (3) Only increase the overland confluence; (4) At the same time increase the channel and overland confluence. And carry out the hour-scale flood simulation application research in Wangjiaba sub basin of Huaihe River. The research results show that compared with the original SIMHYD model, the simulation accuracy of SIMHYD model with addition of confluence is improved, and the simulation accuracy of SIMHYD model with addition of channel confluence and overland confluence is improved the most. In this study, the SIMHYD model can be applied to hour-scale flood prediction and simulation by improving the confluence part of the model, and the simulation effect is better.