Team work mode creates more achievements than individual mode in today's enterprises and thus becomes ever more popular. However, ethical crisis in the team, once emerges, will significantly affect group outcome. The leader contributes to the team's morality so much that ethical leadership has become an important research subject these years. To make clear how much an ethical leadership would affect on the group performance seems both theoretically and practically meaningful. Previous studies usually use social exchange theory to explain the interaction between an ethical leader and his team members. Two shortcomings commonly exist in such researches. First, they mostly focus on the behavior mechanism rather than the cognition mechanism, leading to the neglect over the analysis on and digging into the trust mechanism. Second, they neglected the necessary situational condition in the social exchange process, i.e., only when the two parties follow the same moral protocols will they be able to follow the mutual favored rules required by the social exchanges. To solve these problems, this research constructs a theoretical model and conducts empirical studies in respects of the mediation mechanism and the marginal conditions of an ethical leader's influences on group performances. We firstly, based on four possible explanations, hypothesize that ethical leadership enhances group task performance. Secondly, we reveal the mediation mechanism by introducing trust perspective. According to social exchange theory, reciprocity will happen in a mature social exchange relationship, whereas mutual trust is the key to ensure that such responsibility will be fulfilled. On one hand, ethical leaders have behavioral consistency with his words and benevolence toward others. These characters will affect team members' trust towards ethical leaders. On the other hand, trust towards leaders will enhance interpersonal interaction within team and improve employees' working attitude, and ultimately improve team performance. Therefore, we hypothesized ethical leadership influenced group task performance through trust in leaders. In addition, we examine the moderating effect of group-level moral identity from the perspective of value congruence. When team members have higher moral identity, they will have a consistent moral standard with ethical leader, which produce a coherent behavior standard and mutual trust, resulting in expected group outcome. Accordingly, we hypothesized group-level moral identity moderate the relation between ethical leadership and trust in leaders. Finally, we systematically built an integrative moderated mediation model. Empirically, we collected data of 81 work groups from several Chinese companies (395 members and 81 leaders were included). Regression analysis provided supporting evidence for all the hypotheses. Ethical leadership increases subordinates' trust in the leaders, and further increases group performances. Such effect will be stronger when there is higher group-level moral identity. These findings emphasize the importance of trust in social exchange process, and deepen the understanding of social exchange theory. More importantly, the research outcome will enhance ethical leadership study. Finally, the limitation of our study is discussed. A longitudinal research design and contextual questionnaire should be further developed in the future.