Abstract: The waterjet duct can change the flow field of the stern, and it has a great influence on the resistance performance of the ship. The resistance performance of marine vehicles driven by waterjets is very different from that of conventional ships, so it is meaningful to study the changes to the resistance performance of the ship. We used the CFD software STAR-CCM +, treated the waterjet duct as the appendage and compared the change of the flow field in the stern after the installation of the waterjet duct at different angles. We described the change mechanism of the ship's resistance and resistance components by comparing the change in pressure distribution of the waterjet duct's surface and the flow field around the hull. The results show that STAR-CCM+ can realize the prediction of ship resistance performance because the simulation results achieved perfect accuracy, and it is gradually becoming the development direction of the resistance performance prediction of marine vehicles driven by waterjets. The installation of the waterjet duct will increase the resistance of the ship, which is mainly due to the increase of pressure resistance. In addition, the resistance performance of a ship driven by waterjets can be improved by the optimization of the waterjet duct's angle.