<p>Modular micro–nano-satellite is an emerging satellite system assembled by multiple modules, whose assembly design is a complex process involving the allocation and layout between components and modules. In order to obtain the best mass characteristics, this paper proposes a cascade heuristic algorithm based on Tabu Search (TS) and Improved Differential Evolution (IDE) to solve the assembly design problem of modular micro–nano-satellites. The algorithm adopts the TS algorithm as the first stage, and the components migration and swapping mechanism are used to obtain the optimal allocation scheme. On the basis of the optimal allocation scheme, an IDE algorithm is proposed as the second-stage optimization, which adds the components exchange and adjustment mechanism to obtain the optimal layout scheme. The performance and effectiveness of the proposed method are verified by applying it to a 12U modular micro–nano-satellite. The simulation results show that the proposed method can further reduce the system mass difference (MD) and moment of inertia (MOI), which provides an effective way to solve the assembly design problem of multi-module satellite systems.</p>