In the single chamber- type hydro- pneumatic suspension of construction vehicles,some gas flows into ringcavity with liquid,and the gas dissolution and precipitation in the ring cavity can affect the suspension performanceto some extent.In order to reveal the effect mechanism,a nonlinear mathematical model of hydro- pneumaticsuspension is established on the basis of gas volume in the ring cavity.In this model,a co- simulation method isused to solve nonlinear equations so as to analyze the effect of the gas dissolution and precipitation in the ring cavityon the pressure.Furthermore,an equally- proportional hydro- pneumatic suspension test bench is set up to verify theco- simulation results.Comparison between the co- simulation and experimental results indicates that (1) the pro-posed model can accurately describe the effect of the gas dissolution and precipitation in ring cavity on the suspen-sion performance and the effect should not be ignored in the design and application of this kind of suspension;(2) the gas solubility and the external stimulation play an important role in the effect; and (3) the gas dissolutionand precipitation have a small effect on the suspension spring quality but have strong effects on the impact,vibra-tion strength and durability of internal structure of the hydro pneumatic suspension.