Based on the sprung mass resonance problem of a vehicle with multiple leaf springs， the relationship between the friction and the dynamic stiffness and damping coefficient of the leaf spring is studied. The resonance frequency and amplitude of suspension are measured by road test， the actual force and deformation is simulated on the leaf spring testing machine， and the equivalent friction， dynamic stiffness and damping coefficient are measured with machine. It is pointed out that the main factor leading to the deterioration of ride comfort is the dynamic stiffness which is several times of the designed stiffness caused by friction. The results show that both dynamic and static friction increase the dynamic stiffness of the leaf spring， but the damping is only related to the work done by the dynamic friction. Axial load is positively correlated with dynamic stiffness and damping， while amplitude is negatively correlated with dynamic stiffness. The studied frequency has little effect on the dynamic stiffness and friction. The load data in the testing process is applied to the multi-body dynamic model of the leaf spring to simulate the resonant working condition of the suspension. The average error of the dynamic stiffness， friction and damping coefficient obtained from the comparison between the simulation and the test data meet the engineering requirements. The method is helpful to establish a high-precision dynamic model to accurately predict the handling stability and comfort of the vehicle.