A series of polycrystaline bulk (La1-xRx)2/3Sr1/3MnO3(R=Sm,Tb) over a wide composition range were prepared by two different techniques, and their structure nd magnetostriction effect were studied carefully at room temperature. The X-ray diffraction pattern indicated that the structure of samples transformed from rhombohedral type to orthorhombic phase with decreasing R contents. The sample, composition near the transformation point, had the maximum value of magnetostriction. The magnetostriction may come from the exchange magnetostriction in the samples at room temperature.