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In order to study the quantitative and qualitative traits of hay in flowering stage of forage vetch, under effect of different densities, an experiment was conducted at research field of Faculty of Agriculture, Lorestan University in autumn 2007. The experiment was carried out as factorial based on a randomized complete block design with three replications. In this experiment three species of vetch including (broad leaf, common and woolly pod) were studied and evaluated under three plant densities (100, 150 and 200 plant m-2). Interaction (density in species) showed the highest hay yield with 2268 kg ha-1 was produced in 200 plant m-2 by broad leaf vetch and the lowest hay yield with 724 kg ha-1 in 100 plant m-2 by woolly pod vetch. Moreover, species and density had significant effects on qualitative traits of hay (crude protein percent and yield), percentage and yield of insoluble fiber yield in neutral detergents and (density × species ) interaction as well. In this experiment plant height was under the effect of (density × species), as well as stem diameter under the effect of species.