The article reports a high power burst laser for laser range-finder application.It uses the technology of passive Q switch with crystal of Cr4+∶YAG,in order to achieve the steady burst pulses.With the suitable design of the YAG crystal and the cavity,it can achieve the energy of 800 mJ when the pulse frequency is 10 Hz,it also gives good beam quality.Using the software of CF design to analyze the cooling liquid,it optimizes the design of the structure and enhances the suitability and the credibility of the LASER for possible environment.