Hydro-gas suspension systems cushion shocks and damp oscillations of vehicle hull when it moves on uneven terrain. The hydro-gas suspension provides the vehicle with proper ride comfort due to non-linear characteristics of hydro-gas units. The hydro-gas suspension system can store a large amount of potential energy; accordingly, it can withstand higher shocks than the torsion bar suspension. Consequently, it is preferred to be used in the design of vehicle suspension. In this paper, a mathematical model for hydro-gas unit used in BMR wheeled vehicle is established to evaluate its characteristics using Matlab /Simulink program. The mathematical model is validated experimentally using the data measured for the unit in laboratory using MTS (793) damper test system. The unit is tested using an input sine wave excitation by a frequency and amplitude corresponding to real road conditions.A f floating piston area V 2 volume of upper chamber A p piston area Vo initial volume of gas chamber A r rod area X floating piston displacement v vehicle speed Z main piston displacement a road wave length