Determination of false target’s guarded angle is a necessary step for tricking the semi-active laser guided weapon.Considering some influence factors,such as radiant intensity of laser indicator and jamming,reflected characteristics of true and false target,attenuation coefficient of atmosphere,and so on,the expression of signal suppression coefficient for coming laser-guided seeker was derived,and the computational formula of false target’s guarded angle was established through suppression coefficient.Furthermore,taking diffuse reflection board as an example,guarded angles under different conditions were analyzed.Lastly,based on the guarded angle of diffuse reflection board,the application of diffuse reflection board used as false target during laser trick jamming was ensured from aspects of layout situation,layout stance,layout quantity and coordinating means.The research has a guidance significance for determining the false target’s guarded angle and the application of diffuse reflection board used for false target.