As an auxiliary braking element, hydraulic retarder has the advantages of high braking torque, stable braking and good thermal stability. It has been widely used in heavy commercial vehicles and construction machinery under special working conditions such as heavy load and long downhill. The open hydraulic retarder adopts integral casting process, and the stator is machined on the shell. It not only improves the structural strength of the stator, but also reduces the difficulty and cost of manufacturing. However, due to the limitation of shell structure, the shape of stator blades is generally irregular, which leads to the uneven distribution of hydraulic force in the rotor internal flow field, the imbalance of axial force and the wear of bearings. If the load of the working wheel exceeds the strength limit of the selected material, the hydraulic retarder will easily cause the blade to break when braking at high speed, which is a potential safety hazard, so it is necessary to analyze the blade’s strength. At present, many scholars have studied the hydraulic retarder with regular flow channel structure by CFD technology, analyzed the internal flow field characteristics and calculated the strength. In this paper, the finite element analysis of the internal flow field characteristics of the open hydraulic retarder is carried out by CFD, and the axial force on the rotor is accurately solved. The axial force of the impeller is reduced by punching holes in the rotor blades. The accurate pressure load is also loaded into the retarder model, so that a more accurate strength analysis of the retarder is realized. The simulation results show that the axial force of the rotor decreases obviously after drilling, and the structural strength of the rotor is also within the strength range of the material.of the retarder is realized. The simulation results show that the axial force of the rotor decreases obviously after drilling, and the structural strength of the rotor is also within the strength range of the material.