In order to simulate the real shooting scene and reduce the cost of military shooting training，a laser shooting optical system based on erbium glass laser is designed. The system uses two-stage laser beam expansion to compress the divergence angle of the output beam of the erbium glass laser twice and ensure the output of the beam with the minimum divergence angle. It improves the human eye safety during laser shooting.The divergence angle of the output beam of the erbium glass laser is 15mrad and the diameter of the output spot is ?0.3 mm，the laser beam expansion rate is 300 times， and the beam divergence angle of the system is 0.035 mrad. 1km away from the optical system outlet，the laser spot diameter is about ?120 mm，which can meet the requirements of kilometer shooting training and break through the distance limit of the conventional laser shooting system. The total length of the designed optical system is 364 mm，the structure is simple，it is convenient for engineering，and the application prospect is broad.