The taxonomic study of the Genus Panicum in Thailand was conducted by investigating and collecting the specimens from various parts of the country. All specimens, including those from the herbaria of the Royal Forest Department (BKF), the Development of Agriculture (BK), the Ministry of Agriculture and Cooperatives and the herbarium of the Department of Botany, Faculty of Science, Kasetsart University were identified. The complete description key to species including the line drawing of plants were made. There are 22 species of Panicum, 18 species of them were identified, namely : Panicum antidotale, P. auritum, P. austroasiaticum, P. brevifolium,P. cambogiense, P. coloratum, P. elegantissimum, P. incomtum, P.kerrii, P.longiloreum, P. maximum, P. miliaceum, P.notatum, P.paludosum, P. repens, P.sarmentosum, P. trichoides and P. trypheron, the other four species were unidentified and expected to be the new species or new record. The pollen of some species of the genus were also studied. Most of them are not much different in shape, size, polarity, symmetry and etc. It is found that they are monad, spheroidal, heteropolar, bilateral symmetry and monoporate and the exine sculturing was scabrate.