Haitan Island of Pingtan County was chosen as the study area. Based on Landsat TM image (in 1990) and ALOS images (in 2010), with the support of ArcGIS and Fragstats software platform, the spatial-temporal characteristics of landscape dynamic change and their ecological effects were quantitatively analyzed during the past 20 years (from 1990 to 2010), by using the models of land use dynamic degree and transition matrix of land use types, as well as index method of landscape pattern. The results showed that the landscape pattern of study area had a significant dynamic change in the past 20 years. The land for built-up and settlement place increased continuously in large scale, while farmland decreased obviously. Farmland and forest land were the main landscape types in Haitan Island. The transition between the landscape types was mainly the changes between farmland and forest land, along with farmland and forest land changing to urban (including built-up, settlement place and road). Based on the analysis of class level indices, the patches of various types tended to fragment. At landscape scale, landscape pattern tended to diversification; meanwhile landscape heterogeneity was increased, and the fragmentation degree was deepened. From the spatial changes of landscape ecological effect, the influences of human activities expanded along the roads and urban regions.