Pooideae is the biggest subfamily of Poaeceae with ~3,900 species (34% of Poaceae species), similar in size to moderately large families like Brassicaceae , Rosaceae and Apiaceae, and larger than 96% of angiosperm families. It contains important crops including wheat, barley and oat. So far, however, many of the relationships among Pooideae tribes and subtribes remain unclear or inconsistent relying largely on plastid markers. In this project, we aim to resolve its phylogeny by using hundreds to thousands of low/single copy nuclear genes from transcriptome data. Based on the phylogeny, we further conducted molecular clock analysis, ancestral character analyses, diversification rate analyses, gene duplication detection and molecular evolution of related genes, all these together provide clues to the possible factors of adaptive evolution of temperate grasses.