This paper discusses a problem of the trajectory optimization and it's realization for the maximum flight range of the missile with constraints on the terminal velocity and angle of flight path. The trajectory optimization is resolved with Gauss pseudospectral method, then the optimized trajectory is taken as a standard trajectory for the autopilot to track and realize in numerical simulation flight of the missile. Aircraft guidance law and autopilot design are discussed about the implementation of the optimized trajectory. Two realization methods namely position tracking and acceleration tracking, are proposed and compared. At last, taking the acceleration tracking method as example, this paper analyzes the effects of autopilot parameter changes.