A compact diode pumped slab laser used in long-range pulse laser rangefinder was demonstrated. Using MOPA laser scheme,the maximum output energy of the laser was 250 mJ,the corresponding output pulse width and laser divergence were 12.83 ns and 0.18 mrad,respectively. The laser was used in a long range rangefinder. The ranging distance was investigated theoretically,and the maximum ranging distance could be as long as 50 km. Due to the advantages of long ranging distance,low weight and compact package,the laser range finder could be used in many applications.