Jamming power, the interval of artificial target and the set forward time are the key factors affecting the jamming result. In this paper, the expression of jamming power was deduced, the model of position relationship between real and artificial targets and the missile was established. The relationship of the interval of artificial target with the height of missile seeker and the altitude and azimuthal angle of the optical axis was discussed. Then the interval of artificial target was obtained. Based on analyzing the probability density function of jamming signal and guided signal, the best value of set forward time along with different gate width was found. It can be concluded that decreasing the time stability of jamming signal can increase the probability of jamming pulse into the gate.