Abstract: Acer Linn.，a highly diversified genus with more than 200 species in the Aceraceae，has been an very difficult group in both taxonomical and phylogenetic studies. The infrageneric phylogeny，classification and systematic positions of some species remain unclear for this genus. The main objective of this study was to examine infrageneric relationships of Acer as inferred from molecular evidence against the traditional classification on the basis of the morphological characteristics. In addition，we intended to investigate the systematic position of some controversial species，as well as to reconstruct phylogeny of this genus. In this study，the nuclear ribosomal ITS region and four chloroplast regions（matk，rbcL，trnH-psbA and trnL-trnF）were sequenced or downloaded for 61 species in Acer，representing the 15 sections in Fang' system（1981）. It was indicated that the revisions of Sect. Palmata，Sect. Microcarpa and Sect. Integrifolia in Xu' system（2008）were correct，which were supported by the species clusters. Based on cluster analysis and morphological data，three evolutionary branches of Acer were inferred. Sect. Palmata，Sect. Arguta，Sect. Spicata，Sect. Cissifolia and Sect. Negundo belong to the same evolutionary branch，Sect. Acer，Sect. Ginnala，Sect. Hyptiocarpa，Sect. Integrifolia，Sect. Trifoliata and Sect. Pentaphylla were located in another evolutionary branch，and Sect. Platanoidea，Sect. Macrantha and Sect. Lithocarpa were clustered in the third evolutionary branch. In addition，some morphological indicators，such as sexuality，inflorescence type，leaf shape，and leaflets number were proved important for studying infrageneric phylogeny of this genus. Our results also demonstrated that A. olivaceum should be better treated as a synonym of A. elegantulum，while the systematic positions of A. wardii，A. hookeri，A. yangjuechi，A. prolificum，and A. changhuaense require further study.

Key words: Acer, DNA barcoding, ITS, taxonomy, phylogeny