Abstract: In order to enhance the environmental anti-interference capability for the radius of curvature （ROC） measurement and meet the requirements of use on the production spot, a laser differential confocal curvature measurement system with grating was developed, which used the property, that the zero point of a differential confocal intensity curve corresponds to the focus of objective, to precisely identify the cat-eye and confocal positions of the tested lens, and then used the grating to measure the distance between these two positions, thereby the highprecision measurement of ROC was achieved. Experimental results show that the system has an accuracy of better than 510-6. So it can meet the demand of high-precision measurement of ROC.