Regional landscape ecological security is an important issue for overall ecological security, and also has a great influence on national security and social sustainable development. Based on the products of the Landsat 5 TM images in 1990 and the Landsat 7 ETM+ images in 2005, landscape classification maps of nine cities in the Pearl River Delta (PRD) have been compiled by using remote sensing (RS) and geographic information system (GIS) technology. Using the aggregation index, crush index, landscape shape index, Shannon diversity index, landscape fragility index and landscape security adjacent index, the spatial-temporal characteristics of landscape patterns in the PRD were analyzed. On the basis of these results, the landscape ecological security index was calculated by using projection pursuit which is based on a genetic algorithm, and the landscape ecological security of the nine cities in the PRD was thus evaluated. The main results of this research were: (1) from 1990 to 2005, there was little change in the aggregation index, crush index, landscape shape index, and Shannon diversity index of the nine cities, while the landscape fragility index and landscape security adjacent index changed substantially. The landscape fragility index showed a decreasing trend, but the landscape security adjacent index has been increasing; (2) from 1990 to 2005, the landscape ecology of Zhuhai and Huizhou cities maintained a good security situation, but relatively low values of ecological security were seen in Dongguan and Foshan cities. Except for Foshan and Guangzhou cities, whose landscape ecological security situation improved slightly, the other seven cities had reduced values of landscape ecological security, among which the largest decrease was 0.5193 in Zhaoqing City. The PRD has experienced rapid economic development and intensive human activities in recent years. This study, based on landscape analysis, provides a sound method to discover the alteration of character among different landscape types and to understand the landscape ecological security status. The results of this study might offer important information for regional eco-construction and natural resource exploitation.