Abstract: With excellent isolation performances,hydro-pneumatic suspensions are widely employed as vibration isolation system in many engineering field.The dual-chamber hydro-pneumatic suspension is a modified version of the traditional hydro-pneumatic suspension.The expressions for the equivalent stiffness and damping coefficient were derived from the modeling of dual-chamber hydro-pneumatic suspension expressed by a set of differential equations.Both the equivalent stiffness and damping coefficient show their strong dependency on the excitation frequency and amplitude.Based on the harmonic balance method,the effects of three key parameters,the stiffness of two accumulators and the damping coefficient of throttle,on the equivalent stiffness and damping coefficient were analyzed.The validity of the expression was confirmed through experiment result.