In order to confirm the relationship between launch safeness and piston slippage move and remove the failure by the piston slippage move,the working principle of reciprocating hydraulic balanced launcher and the cause of the piston slippage move were analyzed.The mathematic model was established and simulation model was established with Simulink to realize trajectory mathematical simulation of reciprocating hydraulic balanced launcher.By comparing the result,the effect was more near practice.To different piston slippage moving distance,the model was used to make quantitative analysis of the relationship between launch safeness and piston slippage move.Analysis was conducted on the reason affecting the launching safeness.It provides a theoretical basis for appropriately removing the failure by the piston slippage move.