Abstract: The pollen morphology of 4 species of the genus Alternanthera from China was examined under light and scanning electron microscope. The results show that pollen grains are spheroidal or subspheroidal, apolar, 10—20μm in diameter and with pantoporate aperture; the vestibulum can be circular, elliptic or other shapes; there are some significant differences between Alternanthera philoxeroides and the other 3 species. According to the characters of surface spinulate, granulate of aperture, the density and distribution of spinule, the genus Alternanthera may be classified.