Abstract: The adsorption characteristics of 117Snm(Ⅳ) and 117Snm( Ⅳ )-EDTMP on hydroxyapatite (HA) are studied. The adsorption mechanics of 117Snm(Ⅳ )-EDTMP is also investigated. The adsorption experiments on HA show that 117Snm( Ⅳ ) and 117Snm(Ⅳ )-EDTMP adsorb very rapidly. pH has great effect on the absorption of 117Snm( Ⅳ )-EDTMP on HA, and the acid environment is most favorable, however, the temperature has very slight effect on the absorption. The adsorption model of 117Snm( Ⅳ )-EDTMP is complicated: the quantitative adsorption takes place when the concentration is lower than 60 μmol/g; when the concentration is above this, the adsorption deviates from quantitative one, but still increases remarkably. Then the adsorption mechanics could be understand as the followings: in quantitative adsorption stage, what's adsorbed is the whole-labeled compound; in the deviation stage, what's adsorbed include both the labeled compound and the free 117Snm(Ⅳ) dissociated from it. The desorption experiments from HA show that EDTMP desorbs more 117Snm( Ⅳ )-EDTMP than 117Snm(Ⅳ ).