Abstract: Ecological security is defined as the goal of stakeholders to create a condition where the physical surroundings of a community provide for the needs of its inhabitants without diminishing its natural stock.Recently,the study of ecological security is mainly on the national and regional levels,and focus on landscape orientation comparison.The study of urban ecological security is little,but it is the basis and core of national and regional ecological security.This paper analyzed and referenced the methodology of regional ecological security assessment,taking Beijing as an example.The ecological security situations and trends at time scale (1996～2002) were analyzed,with suggestions on the management of urban ecological security.

Key words: Weak light, High temperature, Fluorescence characteristic, Grain fill, Wheat