A new technique of reducing surface roughness of photoresist grating is presented. In this paper, photoresist melting method, which is low-cost, short-period and easy realization, is presented. In addition, the influence of photoresist melting on the groove profile of the photoresist grating is investigated. Experimental results show that the surface roughness reduces due to surface tension, when developed photoresist is heated to be melting state by this method. In experiment, when the melted photoresist grating is etched by ion beam, the surface relief grating possessing preferable groove profile is obtained on K9 glass substrate, then the surface is evaporated by aluminum using vacuum evaporation, holographic grating with preferable groove profile is successively fabricated.