In consideration of the high experimental demands and higher costs of outdoor experiments for laser-angle-deception jam equipment, the simulation methods and technologies of indoor experiments for laser-angle-deception jam were discussed. A indoor simulation system was constructed in indoor field for detecting the laser-angle-deception jam. By equivalent simulation to the actual environment, the indoor simulation system was established for laser-angle-deception jam weapon detection. The composition and principle of the indoor simulation system were introduced. Then, the relation of the angle between guided missile and object was specially studied, and the influencing factors were analyzed, including the angle of mirror, the distance of device, the distance between baseline and diffuse reflecting screen. On the basis of this, its precision was analysed. Finally, the angle between guided missile and object was measured by using Leica, and its error was computed to be 17″ in azimuth and 13″ in elevation as compared to that from a theory. Obtained results prove the feasibility and validity of the indoor simulation system.