With the rapid development of affective computing and facial expression analysis, it is important to understand trusted facial expressions during human-computer interaction. This paper presents a novel approach for synergetic trust analysis of facial expression. Based on the cooperative mechanism between facial expression features and affective trust evidences, the synergy theory is applied to extend the evidences and to achieve the reasoning algorithm in a proactive environment. The resultant model from cooperative interaction and synergetic dependence evaluation is potentially capable of analyzing the trusted facial expression. Experiments have been conducted to evaluate the rationality of the approach. It is suggested that synergetic trust model can reduce the subjective impacts of overall analysis and perform at a higher credibility can allow the user to further comprehend affective computing with trust factors.