This report seeks to improve Seoul's existing urban planning system through the elements and practices of current Form-Based Code (FBC) in United States. Because Seoul's planning system has similar problems with the conventional zoning practice that the FBC purposes to overcome, the FBC practices in US provides meaningful examples that could help make Seoul's planning system more organized and sustainable. First, this report presents definitions, purpose, background, basic principles and elements of the FBC, and then explores expected benefits and criticism that has emerged from various reports and publications. Second, the Miami, Florida and Denver, Colorado FBC cases are analyzed and assessed to examine its real impact and implications for a citywide FBC adoption. The conclusion of this study provides what should be considered important to an FBC and how to apply an FBC to Seoul, and conclusion of this study.