A method of inspecting an EUV reticle is proposed, which uses an original design layout information to align the plurality of patterns on an image, which is got by scanning the surface of an EUV reticle, such that the defect can be identified and classified according to the aligned patterns. In the scanning process, a step of conditioning surface charge is followed by a step of inspecting surface of the EUV reticle wherein the step of conditioning surface can neutralize the surface charge and the step of inspecting can obtain an image of the EUV reticle. The method of inspecting an EUV reticle also tuning a retarding electrode to attract more secondary electrons such that the greylevels of different patterns may be shown and the defect can be identified and classified.