The distribution of intensity of incident irradiation in photo-resist during exposure is figured out, and it is shown that the pattern in photo-resist on surface with high reflectivity will suffer standing wave due to the fact that the incidence irradiation interferences with the reflective beam from the photo-resist-substrate interface. The higher the reflectivity, the worse the effect of standing wave is, and it is shown that the standing wave will have adverse effects on the profile and the duty cycle of photo-resist grating and restricts the most groove depth. Inserting a layer of anti-reflection coating (ARC) can minimize the effect of standing wave. Experimental results show that it is a good way to use ARC between photo-resist and substrate to attenuate standing wave.