To enhance the mechanical performance of lattice-infilled structures, this paper presents a multiscale topology optimization method based on ordered solid isotropic material with penalization (Ordered SIMP) interpola? tion model for lattice-solid hybrid structure design. The X-shape cubic cell is selected as the basic lattice structure, and polynomial functions are established through numerical fitting to relate the lattice relative density to its physical properties. Then, for macro structure topology optimization, relative densities of the macro elements are employed as the design variables, and a multi-material interpolation model spanning from variable-density lattices to solid is de? veloped based on the Ordered SIMP interpolation. Finally, a multiscale topology optimization problem is formulated to minimize the structural compliance of the lattice-solid hybrid structures subject to a material volume fraction constraint. Numerical examples and mechanical testing are presented to demonstrate the effectiveness of the proposed ap? proach compared with pure lattice-infilled structure designs.