Abstract: Pollinium morphology of five most common cultivated orchid genera（Orchidaceae）were examined with SEM（scanning electron microscopy）. The results showed that thousands up to ten thousands of pollen grainsare aggregated into distinct pollinia. The pollinia presented diversity in shape，from near pear-shaped，near ovate，to oblong oval. The figures of pollen grains are irregular. The tetrad pollen grains were only found in species of Cymbidium ensifolium. Except C. faberi，there are not obvious sticky semiliquid substance covered the pollen grains. The pollinium of the speces studied can be divided into four types based on the sculpturing of exine. There are psilate，near psilate or very obscurely fossete，rough and fossulate or foveolate. There are no aperture on the exinous lay of pollen grains. The pollinium size and sculpturing of exine showed obviously different among the genera and species in this study. Within the genus Cymbidium，the sculpturing of pollinium differed on the species level but not obviously on the cultivated variation level.

Key words: Orchidaceae, Cymbidium, Zygopetulum, Phalaenopsis, Oncidium, Pleione, pollinium morphology, scanning electron microscopy（SEM）