Abstract: Forage species selection plays a prominent role in the process of returning cultivated lands back into grasslands, and determination of adaptive distributing range for forage species according to their biological characteristics together with their surroundings provides basis for decision support for the work. Therefore, this study aims to develop a GIS-based decision support system to help managers to make decision on how to deal with the returned cultivated lands. Combining GIS and forage adaptability model into the system, fuzzy logic was used in the reasoning machanism. Users can get climate data, soil information and grassland class, and refer the adaptive forage species and threir planting and managing technology for the target site as well. In addation, the system also provides adaptability distributing map of 22 forage species. The results show that the decision support system is very helpful for the related manager due to its good decision making ability.