The invention relates to a method for preparing nanometer composite resin mouth repair material. Wherein, it comprises that: prepare water-mellow system; hydrolyzing the silane coupler in acetic acid catalyst to be water-mellow system with coupler; modifying the surface of inorganic nanometer stuff; adding the nanometer inorganic powder into the water-mellow system to be dispersed by ultrasonic wave; washing and drying to obtain the modified inorganic nanometer stuff; preparing resin substrate; adding resin monomer into some dilute agent to be diluted, to form resin substrate; preparing nanometer composite resin; in shade, adding the resin substrate into light initializer and share initializer, to be mixed and added with modified inorganic nanometer stuff; mixing and removing the bubble, to obtain the final product. The invention has simple process and short time, while the product has high mechanical strength.