Polymer matrix giant magnetostrictive composites were prepared by combining Tb0.30Dy0.7Fe1.95with epoxy. The effect of epoxy content and preload stress on the magnetostriction of composites was studied using standard strain gauge technique. The results showed that the magnetostriction of the composites of V alloy∶V E-44=9∶1 was 1070×10^-6 under 1 MPa preload stress. There were very marked effect of the epoxy content and preload stress on the magnetostriction of the composites. The excessive or lesser epoxy content went against the increasing of the magnetostriction for the composites. The composites had the biggest magnetostriction when V alloy∶V E-44=7∶3. The lesser preload stress had a positive effect on the magnetostriction of the composites, and the higher preload stress had a negative effect. The composites had the biggest magnetostriction when the preload stress was 1 MPa.
