Multi-criteria decision analysis provides an effective and valuable method of articulating and structuring deliberations within public participation. Public participation means that citizens are involved in the public decision making that has an effect on them. In order to encourage participation while integrating the deliberative perspectives from various participants in public sector, we should support the participatory public decision making process. Our effort is oriented towards integrating trust-based multi-agent modeling within multi-criteria group decision support systems. Decision makers are modeled as agents and each agent has a role in decision making processes which identified by trust level. In this paper, we propose a framework and model to enhance the success of participation process in participatory public decision making. A simple example is also presented in this paper to give a clarity how the framework and model can be implemented in the real situation.