In order to prevent the pressure impact when the load-sensing hydraulic system was in the fast operating mode,hoisting system of truck crane was used as an example to make analysis.AMESim software was used to build the simulation model of load-sensing hydraulic system which was optimized with test data.The main reason which caused pressure impact was found.Then the existing hydraulic system was optimized. The simulation results and product test data show that: the amplitude of pressure impact can be reduced effectively using the improved hydraulic system with a three way anti-impact valve.