Established an index system for early-warning of ecological security which consists of 12 selected items;the weight of indicators was determined using expert score.Then this system was applied to pre-warn with the use of datum of Minjiang watershed in year 2004 and in year 2008 based on matter element analysis,and got the ecological security warning degree.The results indicated that the whole level of eco-security early-warning in Minjiang watershed was in no warning,and had been in well condition,but in somewhere the eco-environment security was not well.It will vary from section to section.It will be much better in the upper reaches than that in the middle and lower reaches.