A flow equation of aperture under the turbulence state is deduced using the boundary layer theory and a method for analyzing the characteristics of the discal throttle aperture of hydropneumatic spring is presented. The equivalent thickness equation of the slice and the flow capacity distribution sketch are given. The mathematical model of hydropneumatic spring is built according to the above equation and the actual gas state equation. The simulation and experiment of the characteristics are conducted. The results show that the turbulence flow equation is workable and the hydropneumatic spring model is correct, both of which provide references to an accurate damping valve design.