The invention provides a longitudinal static margin designing method for an aerospace vehicle based on the optimal performance. The method comprises the steps: (1) preliminary design of an overall plan of the aerospace vehicle; (2) obtaining aerodynamic characteristic data corresponding to aerodynamic layouts of the aerospace vehicle, to determine focus positions; (3) taking relative positions ofmass centers as optimization variables and setting the differences between the mass center positions and the focus positions being less than the preset threshold as the constraint condition, establishing an overall performance optimization model of the vehicle, to determine the optimal mass center position under the current aerodynamic layout; (4) if the optimal mass center position can be reached, proceeding to a step (5), otherwise, adjusting the aerodynamic layout, updating the overall plan of the vehicle, and changing the relative position relationship between the focus positions and the optimal mass center position so that the optimal mass center position can be reached; and (5) calculating the longitudinal static margin based on the determined mass center position and the focus position. The longitudinal static margin designing method for the aerospace vehicle based on the optimal performance can solve the overall optimization design problem of the vehicle related to longitudinalstatic margin and the overall performance of the aerospace vehicle is improved.