In order to accurately guide on-site workers to quickly accomplish the assembly job of complex products, and reduce the deployment cost of assembly instruction, we propose a publishing method of lightweight 3D assembly instruction for complex products. In this paper, the key frames of assembly motion and the 3D technical annotations in the lightweight model are mapped to the time-based assembly process. Then, the annotated lightweight model and assembly process information are integrated and published into a single 3D assembly instruction document. An assembly instruction publishing example of satellite antenna feed component shows that the lightweight 3D assembly instruction is well instructive and affordable because it provides the interactive simulation of assembly process and time-based display of assembly technical annotations without using expensive computer-aided design (CAD) systems, graphics workstations, or virtual reality equipments. This method gives a full play to the advantages of model-based definition technology and lightweight model, and fills the gap between the process planning and the instruction publishing in the 3D virtual manufacturing environment.