Abstract: Interaction is one of the virtual assembly’s important features and a technique bottleneck. Collision-detection-based interaction cannot satisfy real-time requirement. It is an important approach to let virtual environment perceive complicated object relationships in order to solve the problems in interaction. Here put forward are a mechanism, an interaction mode and a relevant algorithm of face-mating perception. They make virtual assembly break away from collision detection based interaction, so the complexity of dynamic collision detection is avoided. The experimental results demonstrate that face-mating perception has enhanced the virtual environment’s understanding of users intention, and at the same time it has ensured the interaction being real-time, and is an effective interaction assistant in virtual assembly.