Abstract: Suitability analysis could coordinate the conflict between urban development and environmental protection. For suitability index mapping, green space locations were identified in the study area from interpretation of aerial photographs and field surveys, and a spatial attribute information database was constructed from each special graph. The spatial analyst tool in ArcGIS9.3 was used to analysis the factors that influence green space suitability, such as land use, vegetation index, population density, distance from road and water. This study compares suitability index(SI)map which was created by using frequency ratio(FR)and analytical hierarchy process(AHP)approaches to analysis urban green space suitability in Changzhou. Correlation were examined among the models using relative operating characteristic(ROC)and gives the planning advance to green space system of Changzhou. The results showed that the change of weight have little impact to the result of AHP based suitability analysis. The spatial distribution patterns of ecological suitability of Changzhou green space were that western area performed higher suitability, while lower suitability was found in the middle area. The high suitability region were mainly large green space and nursery which accounts for 24.14% of the total area; while the low suitability region was mainly construction land which accounted for 17.75% of the total area. The ROC analyses gave results of 0.724, 0.604, 0.612 and 0.597 for the FR, AHP SI maps.