This paper analyzes the species diversity of the long closed conserved forest(CF) and the degraded forest(DF) caused by human disturbance in northern Fujian Province. The result indicates that the plant species richness and Shannon-Wiener indices in DF communities are similar to that in CF communities. But the species diversity of composition and layer structure had significantly changed. The basis of species-population in community had consequently degraded. There is less rare and extincting species in DF communities than that in CF communities, and the species diversity in CF community is practically different than that in DF community.