In this paper, target acquisition probability of a seeker was introduced first, and then the optimal scanning area and scanning mode were analyzed. The probability of target falling into the seeker's beam was calculated, based on which an one-dimensional scanning mode was selected as the scanning mode. A seeker scanning program was designed for optimal scanning. So, a better acquiring probability can be obtained and this scanning concept not only meets the optimal scanning principle but also reduces the requirement for seeker's technical specifications. The study result can also provide reference for similar homing missile's engineering development.