The calculation of three dimensional dose distributions of radionuclide therapy based on the voxel S val- ues is very important in the nuclear medicine domain. 153Sm is one of the nuclides often used for bone metastasis therapy. The S values of 153Sm in different conditions were calculated based on the program of 3D voxel dose calcula- tion built on the Monte Carlo package EGS4. The influences of both material composition and density on the S value were discussed. It is shown that there are obvious influences of material densities on the S value

and while the den- sity is the same

there are fewer influences of material composition on the S value. The calculation could give some help to the 3D voxel dose calculations for radionuclide therapy. The work also indicated the ranges of error of the S values while disregarding the influence of material density and compositions.