Abstract: With the rapid development of photoelectric sensor technology, the infrared interference technology is required higher. Routine system can not be satisfied with the new demands of energy concentration and good concealment. Based on these reasons, this paper put forward a design scheme regarding of an off-axis double reflector type of laser jamming applied at beam expanding system. It designed and analyzed the optical-mechanical structure of such key parts as the components of off-axis double reflectors, the turning plane reflector and supporting and fixing mechanisms. A special structure design of turning plane reflector was adopted with a view to decreasing the size of the system; the design of micro-stress was adopted for components of both the main and secondary reflectors and the turning plane reflector. Simulation results showed that the first order natural frequency was 46.85 Hz, and stress responses of the structure was also far less than yield limit of the material. After the actual detection, the consistency of two axes was below or equal to 0.3 mrad and the beam expanding ratio obtained was 1:12.01, meeting the requirement of designed technical index.