Abstract: The residual stresses of α Fe and beryllium specimen surface with and without the Mylar film are measured by X2001 stress analyzer. The reason and the regulation of the measured residual stress change are discussed. The results show that the increasement of the calibration distance D for the specimen surface with the Mylar film shiftes the diffraction peak to the lower angle, thus changing the measured value of residual stress. The real residual stress of specimen can be obtained by correcting the measured value of residual stress.