Aircraft’s terminal guidance commonly employs Synthetic Aperture Radar (SAR), whose azimuth imaging capability is affected by the observation angle of the aircraft. Currently, forward-looking imaging is often used in the terminal guidance segment of aircraft SAR. In order to ensure an appropriate angle between the terminal guidance segment of the aircraft and the target, this paper designs a slant angle constraint. Based on the three-degree-of-freedom aircraft model, the pseudospectral method is used for trajectory optimization to verify the effectiveness of the slant angle constraint, and the simulation results are analyzed.