This research focuses on the study of Environment Impact Assessment (EIA) for the new engineering development project of Suao-Hualian Section along the Eastern Freeway. The "Project Definition Rating Index (PDRI) Mode is the quantitative assessment method developed by America's Construction Industry Institute (CII), which is the EIA operation by incorporating PDRI in the road construction. The EIA-PDRI mode is mainly established according to the EIA related laws currently practiced in Taiwan and relevant expert questionnaires. Under such configuration, the Vector Weighing Method is based for setting up the weight between the Section, Category and Element. The verification result of this Research supports that the EIA-PDRI Assessment Mode can help set the preliminary scope of the project development while enhancing the EIA performance.