Abstract: The Effect of the amount of ligand HEDTMP on biochemical properties of 153Sm-HEDTMP is studied. The biochemical properties include partition coeffcient of 153Sm-HEDTMP in n-octanol-water which is measured by shake-flask method,combination characteristic with BSA(bovine serum albumin) which is measured through precipitation by TCA(trichloroacetic acid) and adsorption characteristic on HA(hydroxyapatite) which is measured with the same method used in 153Sm-EDTMP .It is found that ,with the increase in the amount of ligand,partition coefficient of 153Sm-HEDTMP in n-octanol-water decreases,so does combination percentage with BSA,but the adsorption percentage on HA shows a little and unremarkable decrease. Considering the relationships between these three biochemical properties and in vivo metabolism of 153Sm-HEDTMP this study supports the view that an appropriate high amount of ligand should be applied in practical use.