The microstructure and magnetic properties of the Tb0.3Dy0.7(Fe1-xPtx)1.95 (x=0.00, 0.02, 0.04, 0.06, 0.08) alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and resistance strain gauge techniques. It is found that the alloys are the single phase microstructure of MgCu2 cubic Laves when the Pt content is less than 0.06 at%, with a line increase of the lattice parameters with the increase of Pt content. But the magnetostriction coefficients decrease with the increase of Pt content, and increase with the increase of external magnetic fields. When the alloys were heated for 4 h at 950 ℃, a better magnetostriction effect is obtained. A small amount of RFe3 phase exists when the Pt content is 0.08 at%.