Quantitative assessment of human activity intensity was a prerequisite for analyzing impacts of human activity on ecosystem as well as assessing the evolution of ecological environment. A model is built based on GIS in this paper to construct a quantitative evaluation framework of human activity intensity. Firstly, 13 human activities indices such as GDP per capita, total industrial output value, annual electricity consumption, population density, the number of business units were selected and a set of human activity index system referring to economic, humanistic, social aspects was established. Then, the Analytical Hierarchy Process method was employed to determine the weights of each human activity indicator. Finally, based on the spatial analysis function of GIS, human activity intensity of the Pear River Delta was exemplified. The human activity intensity of nine cities in the Pearl River Delta was calculated in 1990, 1995, 2000 and 2005. The results indicated that human activity intensity of the Pearl River Delta increase gradually temporally whereas decreased from east to west spatially.