The interstage cushioning characteristics of telescopic hydraulic cylinder will directly affect the stability and safety of hydraulic system.With a sample of threestages hydraulic cylinder,a 3D and timeaccurate computational fluid dynamics (CFD) based on moving grid technique and UDF technology,also including the friction between the piston and the inner cylinder,was used to simulation the hydraulic oil flow field and piston motion characteristics during the retracted phase.The results show that cylindrical slit throttle has significant throttling effect during the buffering phase,but the retract process is long,accompanied by simultaneous movement of two stages; there is a large sudden change in pressure and acceleration during the multistage cylinder change,resulting in hydraulic shock and vibration.The simulation results provide reference for the optimal design of the buffer structure of telescopic hydraulic cylinders.