Abstract: On the basis of checking literature and the specimens concerned, and the field working of the ferns in 33 sample sites in Shanghai, 50 species of the naturally distributed ferns belonging to 23 families, 33 genera have been recognized. The introduced and cultivated species and the species that might be extinct have been discussed. Two-way Indicator Species Analysis (TWINSPAN) and Canonical Correspondence Analysis (CCA) were used to analyse the relationships between the distributions and its environmental factors of the ferns. The results showed that 3 groups of sites could be identified: group 1 including the sites at center of the city has 0 to 4 species; group 2 including the sites at suburb of the city has 0 to 8 species; group 3 including She Mountain Island, She Mountain area and Da Jin Mountain Island with more than 26 species are the areas which have the most rich diversity of fern. The results reflected that habit, coverage and disturbance are main environmental factors for the fern growth in Shanghai.

Key words: Shanghai, ferns, distributional features, environmental factors