Based on the previous researches on Chinese mandarin triphone model and co-articulation, a context-dependent visual speech co-articulation model is proposed in this paper. Our presented model focuses on the visual effect of Chinese mandarin coarticulation. In order to get the key synthesized lip shapes in continuous speech, the rule set of the visual speech co-articulation is constructed and the phones? corresponding visemes weights are calculated by the quantized rule set. We synthesize a sequence of phones? corresponding lip shapes by using our muscle-based facial model. To produce realistic speech animation, a learning-based approach is used to acquire optimal synthesized transition lip shapes between two phones from all possible selections.