Abstract: In this paper, 52 species of the genus Scenedesmus from China have been studied by means of numerical taxonomic methods. Twenty-five morphological characters which are all dual characters were adopted. The result produced by the twoway indicator species analysis (TWINSPAN)showed that 52 species may be divided into 5 types:1) cells oblong, elliptical or oval, with denticular, brevispines, verruca or granulate at two poles of cells and without long spines; 2) cells with long spines and with or without other ornament on cell wall; 3) cells without long spines and with denticular, verruca and ridge not only at two poles of cells but also on free cell wall; 4) cells with polar nodules or thickenings but not obvious and 5) cells fusiform,acicular or lunate, smooth or with small ornament on cell wall. The taxonomy in the genus was therefore discussed.