An emotional interaction system is designed by using the theories about affective computing in this paper, which includes the emotional information capturing, machine emotional model and emotional expression. This paper focuses on the problem of building machine emotional model, not only gives the basic definitions of personality space, mood space, and emotion space, but also establishes the quantitative relationship of personality mood and emotion. At last, this paper builds a machine affective model which can reflect the transformation law of the mood, emotion and personality. Related simulation results show that the model can effectively simulates the change law of human emotion. Finally, this paper designs the software interface of the emotional interaction system.