In this paper, a two-loop control scheme is proposed for the identification and compensation of homing missile guidance. The inner-loop adopts the realistic true proportional navigation design (Yang and Yang,1996) for missile guidance without considering the target's maneuver, while the outer-loop is to construct a genetic algorithm for identifying and cancelling the target's maneuver. Although the target's maneuver may have various types of motion, an on-line genetic algorithm is proposed to learn the target's maneuvering behavior which can be any piecewise continuous function. A compensation control scheme is also implemented to simultaneously cancel the effect of such unknown maneuver. Simulation results demonstrate that the proposed on-line genetic algorithm base control law can achieve good maneuver compensation even under the conditions with measurement noise. Moreover, the coefficients of maneuver are found to be decided exactly if the maneuvering function is predictable.