The seed external morphology and seed coat pattern of 11 genera and 22 species of Melastomataceae in Taiwan were studied by dissecting microscopey and scanning electron microscopey. According to the seed size, the result showed that the length and width of seed is different inter-generically. The biggest size is the seed of Memecylon while contrast to those of the other genera. The seed shapes could be divided into 8 types. They are liner-lanceolate, cuneate, fusiform, reniform, cochleate, triangular, obovoid and parallelogram respectively. Except that of the Sarcopyramis, the seed shape is rather stable intra-generically. The seed coat could be classified into 6 patterns. They are verrucate, rugose, smooth, tuberculate, granulate, and colliculate respectively. The seed colors are egg-yellow, brown, nut-brown and reddish brown. The difference of seed morphology is obvious inter-generically, and the difference of seed coat patterns is extinctive intra-generically.