Taking forest ecosystem health early warning in the North Ditch,Hebei Province as the main line,early warning indicators of forest health were firstly filtered by the method of quantitative analysis,then early warning indicator system was identified.Next,early health warning model off orest ecosystem based on the basic principles of BP neural network was established,and then it was used to make early warning on the health of forest ecosystems.The results showed that North Ditch forest ecosystem was in good health,in the whole,the North Ditch in the range of the green and blue alert.