The invention relates to an anchor sealing method of a prestressed anchor recess, belonging to the technical field of architecture. The method adopts the following steps: (1) cleaning the anchor recess after the tension of an orbital plate; (2) infusing hot-melt modified sulfur mortar into the anchor recess to cause the hot-melt modified sulfur mortar to be level with the side surface of the orbital plate at the opening of the anchor recess; or pre-casting concrete to 1/3-1/2 of volume of the anchor recess, and then infusing the modified sulfur mortar to be level with the side surface of the orbital plate at the opening of the anchor recess. The modified sulfur has higher compressive strength, the hot-melted mortar is firmly bonded with the concrete of the inner surface of the anchor recess, the structure is compact without cracks and can not crack and shrink after cooling, and the modified sulfur also has the characteristics of good performances of impermeability, frost resistance and corrosion resistance. Steel bars are compactly sealed in a space isolated with air by the modified sulfur and can not generate any corrosion. The method just needs one-time construction and does not need specific conservation and anti-corrosion treatment, so the method is very simple and reliable.