The assessment index system for ecological benefit of public welfare forest in Shanghai was firstly established using AHP method. The index system was defined as total objective layer, criterion layer consisted of seven items, and index layer composed of thirty indexes. The weights of the ecological functions such as rnicroclimate improvement, air purification, wind prevention and noise reduction, were obviously higher than other ecological functions. They were 0.24, 0.2 and 0. 19 respectively the result were consistent with high industrialization and future development goal of Shanghai. It also had an effect on guiding the construction of public welfare forest in Shanghai.