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.