There has been an increasing concentration of population in the Seoul Metropolitan Area (SMA) since the 1960s. As a result, approximately 50% of the country’s total population currently resides in the SMA. Such a high density of the population has resulted in urban sprawl, which in turn has led to various problems. Subsequently, the government has implemented a number of urban management policies, and the greenbelt is the representative one. However, there are still various problems due to the development of new towns to accommodate the expanding population. In this study, the urban growth of the SMA was predicted using Cellular Automata method. This is one of the techniques used in the forecasting of urban growth to determine differences between scenarios that involve the existence or nonexistence of greenbelt and other restriction factors. Moreover, the population density was derived by the Auto-Regression model to estimate three dimensional structure of the SMA. Next, the estimated population was used as a coefficient to calculate the emission of atmospheric pollutants. The results of the urban growth prediction determine that the greenbelt works effectively to prevent urban sprawl, restricts the concentration of population, and has a positive effect on the air quality of the SMA.