In this study, we report the genome sequence of Salix suchowensis, a shrub willow closely related to poplars.A total of 303.2Mb genome sequences were assembled with 23.8-fold of 454 single and mate-pair reads and 231.1-fold of Illumina pair-end reads.We predicted 26,599 protein-coding genes and the assembled genome was highly collinear to the poplar genome.Compared with Populus trichocarpa, this Salix specieshad substantially smaller genome size and lower gene number.Genomesacross the two lineages shared the most recent Salicoid duplication, and the more ancient duplications common to Arabidopsis and other dicots.Gene cluster analysis for these two lineages indicated that more extensive loss of genes underwent in willow than in poplar.GO enrichment further showed that willow retained genes that were generally more pleiotropic than poplar genes to balance its heavier loss in genes number.SalixandPopulus began to divergearound six million years after the Salicoid duplication.This study also found that S.suchowensis had higher substitution rate than P.trichocarpa, perhaps due to its earlier sexual maturity.The availability of a Salix genome, alongside that for P.trichocarpa, increases our knowledge of the evolution of the Salicaceae and provides a means for comparative genomics between these woody perennial species and the other sequenced model plants.In total, these resources will be useful for dissecting themechanisms and pathways that control woody traits in Salicaceae, and should help to maximize the efficiency of these genera as woody biofuel crops.