Genetic algorithm (GA) was used to solve the multi-objective non-linear optimization design of a hydro-pneumatic spring. To develop the genetic algorithm of the optimization of hydro-pneumatic spring, a weighted sum was used to normalize the four objectives of ride comfort, suspension stroke, road holding and road friendliness with fixed weight, linear fitness scaling was used to enhance the global search ability of GA, and adaptive penalty method was used to handle the constraint conditions besides the range of design variables. Optimization design examples of 2 and 5 design variables were practiced, analysis based on testing and simulating shows that the comprehensive performance of the hydro-pneumatic suspension increases by 50.66% and 118.18% respectively comparing with the non-optimized one, which confirms the validity of this method.