Abstract: 22 kinds of seed oils were extracted from 8 genera of the family Ulmaceae in China The seed oils were examined for their characteristics and fatty acid compositions by gas liquid chromatography. The fatty acid compositions of these oils were found to fall into two classes. Some genera (such as Ulmus, Zelkova) contain mainly lower saturated acids, in which the chief acid is capric acid 10:0, while the genera (such as Celtis, Pteroceltis, Aphananthe, Trema, Gironniera) contain mainly unsaturated acids, in which the chief acid is linoleic acid 18:2. Hemiptelea davidii (Hance) Planch contain however either certain amount of short-chain saturated acids or higher unsaturated acids, it appears a intermediate genus between the two classes. According to the component acids we support that the Ulmaceae be split into two subfamilies. The genera arrangement based on the component acids corresponds basically with the view based on mophological characters and flavonoids found in leaves of Ulmaceae, but there are some discrepancies in certain genera, for example, the Aphananthe should beplaced in Celtoid instead of Ulmoid by the present study.