This article, from analyzing the environmental disputes of the 3rd stage of Central Taiwan Science Park (CTSP), discusses the role of public participation in the environmental decision making. The Environmental Imapct Assessment (EIA) review process for the 3rd stage of the CTSP, which was regarded as one of the flagship plans for Taiwan high-tech development, started in the end of 2005. In order to accelerate the plan, Taiwan’s Executive Yuan demanded that the CTSP’s environmental impact assessment (EIA) case be approved as quickly as possible. However, the strong pressure from the administration brought about the protest of some independent EIA Review Commissioners and public attention. Although the EIA review for the project finally got a conditional approval, controversies remained as the pressure of policy reform to address environmental concerns continued at both central and local levels. In this case, the concerned local residents and environmental groups demonstrated the very high degree of public participation as they attended all the related meetings and voiced their concerns. The EIA conclusions were thus made in response to those concerns and demand the developer to hold public meetings, form environmental monitoring groups, and conduct health risk assessment to enhance its communication with local residents. Such requirements offered an opportunity for us to examine the role of public participation and explore its contribution and potential influences in the EIA process. From the STS perspective, this paper further argues that it is necessary to recognize the current limitation of scientific assessment and openly include public deliberation in the EIA review processes. In conclusion, the paper recommends that the EIA review should actively adopt the hearing process in order to encourage public dialogues, bridge the knowledge and policy, as well as clarify the arguing points. Only with such procedural improvement, the quality of the EIA and environmental democracy could be both enhanced.