Crossed grating stuck to metal surface was used as a strain sensor in the present work,and stress as well as strain were then investigated by accurately determining the change in the position of diffraction spot before and after deformed.A hardware testing system for linear CCD array,data gathering and processing was therefore developed for this purpose.Experimental results showed that the system has a good accuracy and can be used to measure stress and strain of metal surface in a real-time and quantitative manner.