Trajectory optimization problem of anti-ship missile synthetic aperture radars (SAR) terminal guidance is researched using an improved real-coded genetic algorithm. The effect of trajectory and look angle to the azimuth resolution of the missile-borne synthetic aperture radar seeker was analyzed, and constraints of imaging of the missile-borne SAR to missile flying trajectory were given. Missile lateral acceleration was regarded as optimized variable, and objective function about the dwell time and the desired azimuth resolution was established. Simulation results show that the optimized values of objective function by the improved genetic algorithm reduce more sharply than by standard genetic algorithm, so the optimal solution can be obtained more quickly.