For human-computer interaction, virtual characters become more and more important in many applications. However, the facial animation developed in the past years generally focused on the simulation of human face. For animation and interaction in virtual world the emphasis should be extended to general objects with human-like faces. We propose four parameter-based lip models that can apply the lip motion to general objects with lip-like meshes. We analyze the characteristics of lip motions and define four different lip models: inflexible-cylindrical model, flexible-cylindrical model, inflexible-square model, and flexible-square model. The parameters of lip motion in different lip models are extracted from the original real facial image sequence with lip motion. These parameters are then used to generate a lip-motion simulation system for general objects. Using the system, the user can apply the lip motion to any meshes by simply defining the lip model.