Abstract:The pollen morphology of 19 species belonging to 5 sections of Ulmus L. (Ulmaceae) was studied. All the species were observed under SEM and partly TEM, in which, 15 representative species of 4 sections were examined and measured under LM with statistical method. 1. The pollen grains of the genus are heteropolar, suboblate to oblate, polygonal to rounded or irregular-shaped in polar view; the pollen sizes are 20.8–30.9 μm × 22.1–49.4 μm; there are 4–7 pores located in equator or subequator; the pores are circular, subcircular to shortly furrow-like or sometimes irregular in shape, averaged 1.8–6.01μm × 1.4–3.5μm in size, with pore membrane and usually with pore annulus; the exine thickness averages 1–2.6 μm; the ornamentation is verrucate, striate-rugulate, cerebroid, coarse-ornate and fine-ornate; whole pollen grain is covered by a great number of very small processes(granules). In the structure of exine there is no typical columellae. 2. The various sections, even their species of Ulrnus L., may be distinguished to some extent by the characters of pollen morphology particularly based on the aspect of statistics. 3. The treatment of the Gen. Chaetoptelea Liebm. as a Sect. Chaetoptelea (Liebm). Schneider of Gen. Ulmus is supported by the pollen morphology of U. elongata L.K.Fu et C.S.Ding discovered in China. And Sect. Chaetoptelea is more primitive than Sect. Blepharocarpus. 4. About the systematic arrangement of the sections of Ulmus, the pollen information shows that the Sect. Microptelea is the most primitive one in Genus Ulmus.