Abstract: The rose scanning technology is utilized for optical system imaging detection to improve the electro-optic countermeasure capability of the IR seeker in precision guidance system. The design of the linear array detector and Cassegrainian optics is the critical part of the work. The calculation of the target position was realized by introduction of the computer processing of image frames. The technical scheme is introduced and several key techniques are analyzed. The prototype was made and tested in the lab. The test data and simulation results show that its antiinterference capability against infrared decoy is improved. The experiment indicates that the seeker can meet the requirements of the precision-guided weapons, such as portable air defense missiles and shipborne terminal-guidance air defense missiles. The design concept is proved feasible.