The concept of"Ecological Defence"is advanced from the ecological construction practice in China,and has been used only for several years.However,there has not an agreed understanding in academic circle.This paper discussed the functions and characteristics of ”Ecological Defence”,based on its definition made by the authores in another paper.In the author's point of view,the function of ”Ecological Defence”is a kind of protecting effect to the human beings’living environment,which the eco2system of”Ecological Defence”produces in its evolving process.It represents in retarding and purifying of the eco-system of”Ecological Defence”on negative factors,and protecting and conserving on the positive factors.According to the aim of ecological construction,the function of”Ecological Defence”can be divided into purifying function,adjusting and retardarcing function,soil conserving function,water manipulating function and biodiversity conserving function.