This work aims to establish the landscape ecological countermeasures to improve the sustainability of urban mountain forest and to enrich the biodiversity in twenty mountains of the Seoul Metropolitan City. Landscape ecological analysis was conducted based upon various criteria, such as area and elevation of mountains, flora, naturalized plants, vegetation, forest types, mountain trails, and public facilities. Various measures were suggested for the better maintenances of floristic diversity, introduced plants, vegetation and forest types of urban mountain forests. Sustainable recommendations for land use adminstration were developed for the preparations of a climate change-adapted urban mountain forests, as well as rational managements of ecosystem, walking trails, and public facilities within mountain forest. Rich and diverse natural vegetation as well as high floristic diversity were reported at mountains with higher elevations, larger area size, and rich landscape diversity. Mountains with low elevation, small size with easy public access, however, might require an urgent action to decrease the burdens by anthropogenic disturbances and urban development.