The invention relates to a three-dimensional molding method. Photosensitive resin in a resin groove is irradiated by a surface exposure imaging device and solidified to be molded on a sunken molding platform; the photosensitive resin is pretreated before being subjected to stereo lithography apparatus, thereby reducing the content of dissolved oxygen in the photosensitive resin. The method omits the conversion process form a molding solid-air interface to a liquid photosensitive resin-air interface, thereby greatly increasing the efficiency of three-dimensional molding and also avoiding a complex device structure.