This paper presents a taxonomic study of Hedysarum petrovii (Leguminosae) and some related species based on field observations,examining of herbarium specimens and leaflet venation.The results showed that:Relatively stable differences between H.petrovii and its related species are shown by the morphology of floral organs.H.petrovii differs from H.brachypterum by having bractlets 1~2 times as long as calyx tube,standard as long as keels,while the latter has bractlets 0.5~0.8 times as long as calyx tube,standard 0.8 times as long as keels.H.petrovii differs from H.gmelinii and H.ferganense by having wings 0.3~0.5 times as long as keels,while the latter two both have wings 0.7~0.8 times as long as keels.Leaflet of H.petrovii has a venation with weak primary vein,unbranched secondary veins,many reticulated tertiary veins outside secondary vein loops,and with or without compound intersecondary veins,which is similar to that of H.brachypterum and H.gmelinii.Whereas the leaflet of H.ferganense has a venation with stout primary vein,many branched secondary veins,a little reticulated tertiary veins outside secondary vein loops,and with visibly simple intersecondary veins.Additionally,characters of leaflet venation may be informative on the discussion of intersectional relationship of the genus Hedysarum.