Abstract:(Nd0.6Sr0.4MnO3)1-x/(CrO3)xwith x=0.0–0.030 step 0.005 weight% composites have been prepared by the solid state reaction process. The X-ray and scanning electron microscopic manifest that all composites are a single orthorhombic phase and there are no CrO3 grains separated from NdSrMnO matrix. The electrical measurements have revealed an increase of resistivity and a decrease of metal semiconductor transition with increasing CrO3. The composite x=0.025 has largest magnetoresistance nearly one hundred percent at room temperature.