The invention relates to a preparation method for a decayed tooth filling and repairing material and belongs to the technical field of dentistry restoring. According to the preparation method for the decayed tooth filling and repairing material, fresh ox bones serve as raw materials to prepare natural hydroxyapatite powder, and the natural hydroxyapatite powder is combined with casein phosphopeptides; then silicate glass powder is subjected to hydrofluoric acid surface roughing treatment, nanometer titanium dioxide and aluminum fluoride are used to be combined with the silicate glass powder, and modified glass powder with a good antibacterial property is prepared; and finally the modified glass powder, polyacrylic acid, itaconic acid, calcium fluoride and the like are ball-milled into a cement, and the cement and the composite natural hydroxyapatite powder are ball-milled to prepare the decayed tooth filling and repairing material. According to the preparation method for the decayed tooth filling and repairing material, the antibacterial property is improved through titanium dioxide and fluoride ions, and the cementation property of the cement is improved, so that the prepared decayed tooth filling and repairing material is tightly attached to the dentin surface, a hydroxyapatite layer is deposited, dentin remineralization is achieved, a firm and compact protective layer is formed, and decayed teeth are effectively restored.