Mainly due to their economic importance, genomes of 10 legumes, includingsoybean, wild peanuts, barrel medic, etc, have been sequenced. However, afamily-level comparative genomics analysis has been unavailable. With grape andselected legume genomes as outgroups, we managed to perform a hierarchical andevent-related alignment of these genomes and deconvoluted layers of homologousregions produced by ancestral polyploidizations or speciations. Consequently, weillustrated genomic fractionation characterized by wide-spread gene losses after thepolyploidizations. Notably, high similarity in gene retention between recentlyduplicated chromosomes in soybean supported a likely autopolypoidy nature of itstetraploid ancestor. Moreover, though most gene losses were nearly random,largely but not fully described by geometric distribution, we showed thatpolyploidization contributed divergently to copy number variation of importantgene families. Besides, we showed significantly divergent evolutionary levelsamong legumes, and by performing Ks correction, re-dated major evolutionaryevents during their expansion. The present effort laid a solid foundation for furthergenomics exploration in the legume research community and beyond. Wedescribed only a tiny fraction of legume comparative genomics analysis that weperformed, and more information was stored in the newly constructed LegumeComparative Genomics Research Platform (www.legumegrp.org).