Three-dimensional model–based virtual assembly process planning plays an important role in assembly design of complex product and is typically time- and resource-intensive. There are limited effective solution frameworks for delivering the three-dimensional model–based assembly process information to assembly field in order to directly guide the assembly tasks on site. A cloud service architecture for mobile three-dimensional model is proposed to address these challenges. Under this cloud computing architecture, this article introduces a dynamic assembly simplification approach, which regards the virtual assembly process of complex product as an incremental growth process of dynamic assembly. During the growth process, the current-assembled-state assembly model is simplified with appearance preserved by detecting and removing its invisible features, and the to-be-assembled components are simplified with assembly features preserved using conjugated subgraphs matching method based on MapReduce. The proposed approach has been tested on several cases, and the results show its feasibility and superiority.