Hydraulic hammers are widely used in road building, port building, mining, civil engineering, etc.The first hydraulic hammer was developed in German in the late 1950s and used in civil engineering.Since then, many different types of hydraulic hammers have been developed around the world.In China.some good hydraulic hammers are also produced now, but many high-quality hydraulic hammers used in China now are imported from abroad.So there is need to develop some new hydraulic hammers which can be used efficiently and reliably in China.To develop new hydraulic hammers needs to study dynamic characteristics of them when they are working.