Based on the "pressure-state-response" conceptual framework, an evaluation system is proposed to study landscape ecological security dynamics from 1988 to 2005 in Dongguan City, a fast-growing city in Guangdong Province, China. The pressure index, which describes the pressure that human activities exert on the environment, consists of urban development intensity, population density, distance to major transportation routes, distance to nearest city center and distance to nearest town center. The landscape security state index, which relates to the quality of the environment, is composed of landscape patch density, ecological service value, and landscape vulnerability. The response index, which reflects the reaction of human beings to landscape dynamics, is defined as adjusted intensity of natural reserve districts, forest, park, and crop lands. The evaluation units are Landsat TM pixels and the fundamental data set is obtained by classifying raw TM data. Transportation and city-center location data are obtained from topographic maps. Population, environmental protection, planning, and other data are obtained from the Dongguan statistical yearbook and the Dongguan Department of Environmental Protection. The results for Dongguan City indicate that the pressure index was 0.317, 0.394, and 0.472 in 1988, 1997 and 2005 respectively, which means the landscape pressure increased from 1988 to 2005. The landscape security state indicator was 0.473, 0.406 and 0.365 in 1988, 1997 and 2005, which means landscape security became more insecure. The response to ecological security dynamics was steady from 1988 to 2005. The weighted sum of the pressure index, the landscape security state index, and the response index is the integrated ecological security index which was 0.497, 0.436 and 0.395 in 1988, 1997 and 2005. In short, ecological security declined from 1988 to 2005. The districts with middle-low ecological security expanded outwards from primarily town center locations in 1988 to outlying urban areas and along major transportation routes by 2005. The high ecological security districts, which consist of reservations, forest land, parks, and rivers, were steady from 1988 to 2005. The study indicates that the pixel evaluation unit based on 1 km×1 km neighborhoods is useful for calculating urban development intensity and landscape patch density, and in smoothing the ecological security grade boundary.