Abstract: To remove dissymmetry of the movement of monitor image under some conditions when image guided missile adopting guided search,two factors causing this dissymmetry are found,viz,the angular velocity of line of sight and the lead speed of the missile.According to the two factors the parallel search law is modified to form a new parallel search law based on dissymmetry.Simulation results showed that by adopting the dissymmetrical parallel search law dissymmetry of the movement of monitor image can be removed which is very helpful for the shooter to acquire and capture targets.