To improve the reliability and service life of wet clutches in heavy-duty vehicle transmission systems, a wet clutches torque model considering interface contact state was established. The influence of different parameters on the clutch torque characteristics was studied through the model. Firstly, a simulation and modeling approach was employed to simulate the wet clutch, incorporating interface contact state parameters,and establishing a wet clutch oil charging model and a combination model. Secondly, a wet clutch torque test was conducted on the SAE#2 test bench, and the simulation results were compared with the clutch test data to verify the effectiveness of the simulation model. Finally, the influence of oil pressure, oil temperature, and disc shape on the wet clutch torque characteristics was studied using the combined model. The findings indicate that model considering interface contact states has higher accuracy compared to traditional models, with an improvement of 22.30%. As the control oil pressure decreases, the total torque of the clutch decreases. When the pressure decreases from 1.5 MPa to 1.0 MPa, the peak torque decreases by 22.38%, and the braking time extends by 46.05% simultaneously. The temperature of lubricating oil has a certain degree of influence on the viscous torque and frictional torque of the clutch. The higher the temperature, the smaller the viscous torque, the greater the frictional torque, and the overall braking time slightly decreases. The impact of friction disc shape on clutch torque is mainly reflected in the time of torque generation, and an increase in disc shape leads to an increase in clutch braking time.