Abstract The genus Machilus comprises about 100 species. They are distributing over the tropics and the subtropical zone, mainly in Easten Asia. Eight species and one variety are native plants of Taiwan, including M.konishiiHayata, M. kusanoi Hayata, M. mushaensis Lu, M. obovatifolia (Hayata) Kaneh. et. Sasaki, M. obovatifolia var. taiwuensis Lu & Chen, M. philippinensis Merr., M. pseudolongifolia Hayata., M. thunbergii Siebold & Zucc. and M. zuhoensis Hayata. Machilus japonica Siebold & Zucc. is regarded to be native in Japan, Ryukyu and Korea, but not native to Taiwan. Due to the morphological similarities among several taxa, species identification was a difficult task in the past. Although many scholars have worked on this topic, there are still many unresolved issues left, especially the relationships among M. japonica, M. pseudolongifolia, M. kusanoi, M. zuihonensis and M. mushaensis. This study aims to study Taiwan Machilus taxonomy with an emphasis on a detailed morphological study. In addition, essential oils, DNA sequences and isozymes were also studied. The results are list as follows: 1. Morphological taxonomy: Machilus japonica, M. pseudolongifolia., M. kusanoi, M. zuihonensis and M. mushaensis can be firmily classified into 5 taxa by morphologic characters. 2. Essential oils of leaves: The data of essential oils ca differentiate the closely related species, M. japonica, M. pseudolongifolia, M. kusanoi, M. zuihnensis and M. mushaensis from one another. The data also indicated that M. konishii is better placed in the genus Machilus than in the genus Nothophoebe. 3. DNA sequences: The sequences of the AG1 introns data clearly indicate that M. japonica is distinct from M. pseudolongifolia and M. kusanoi. 4. Isozymes: The data of isozyme analyses can distinctly distinguish the closely related species, M. japonica, M. pseudolongifolia and M. kusanoi. The data also can separate the closely related species, M. zuihonensis and M. mushaensis from each other. With the above data, the author believes that there is no naturally distributed M. japonica in Taiwan and the name M. pseudolongifolia should be used. Machilus pseudolongifolia, M. kusanoi, M. zuihoensis and M. mushaensis are all endemic to Taiwan and are morphologically diistinct. However, the DNA sequences of tested marker genes analyzed indicated that genetically they are not well differentiated. The differences among the DNA sequences of these species were not significant could be due to the possibly relatively short divergent time. Totally, eight indigenous species and one variety of the genus Machilus of Taiwan are recognized. For each species, a morphological description and classification treatment are provided; also included are geographical distribution, ecology, citation of exsiccatae, illustrations and images of type specimens etc.