Abstract: In this paper,a lightweight design technology and methodology of aircraft assembly jig is studied.Sizing optimization is carried out to ensure the jig rigidity based on the cross-sectional dimensions of the constitutive beams.Considering the structural complexity of the assembly jig,the deformation control of specific positioning points,deformation coordination as well as the discrete values of cross-sectional dimensions,in this paper,we propose a multi-model and multi-load case design optimization method based on the genetic algorithm(GA).This method takes into account the self-assembly manufacturing process of the jig and the product assembly process and aims at solving discrete problems.