Abstract:In this paper, a new modified Shannon-Wiener index for measuring species diversity is established by using fractal theory, and the evenness formula is deduced. The new indexand the evenness were used in measuring the species diversity of Castanopsis carlesiicommunity with an area of 100 m2 to 1500 m2 in Wuyishan National Nature Reserve. Theresults showed that the new index could objectively reflect the property of species diversity,and that is worthy of application in practice as a new model.