Abstract: Model-Based Definition (MBD) technology provides an effective approach for the digital definition of manufacturing processes in complex mechanical products, and its comprehensive integration of assembly process information serves as a prerequisite for digital design. To address disorganized information structures and poor visualization in current modeling, an integration and visualization method based on the Skeleton Line-Interaction Feature Pair (SL-IFP) is proposed. This method adopts skeleton line model to macroscopically define the spatial layout and assembly paths among assembly units, and combines Interaction Feature Pairs to precisely express the geometric fits and constraints among components within the assembly units, thereby realizing the structured integration and representation of assembly process information. Finally, the feasibility of the proposed method is validated using a diesel engine crank-connecting rod mechanism. The research findings can provide a reference for the digital definition of assembly process elements in complex mechanical products.