The invention discloses a grease ointment which contains the following materials: vegetable oil, lanolin, vaseline, polyvinyl alcohol, sodium carboxymethyl cellulose, gumacabic powder, xanthan gum, gelatin, dextrin, bentonite, white carbon black, peregal, sodium dodecyl benzene sulfonate, sodium benzoate, polyethylene glycol, n-butyl alcohol, 70 percent of thiophanate-methyl, flusilazole, tebuconazole, an organic solvent, water-soluble substance containing amino acid, and water; the invention also discloses a preparation method of grease ointment, and an application of the grease ointment in sterilization and promotion of healing of rot scar of apple trees. Field experiments show that the grease ointment provided by the invention is harmless to cortical tissues of trees, can promote quick healing of rot scars and kill rot pathogens of cortexes and xylems; the effects of sterilizing and improving healing are greater than the effect of conventional drugs so as to prove that the grease ointment is suitable for rot scar healing and wound protection of the apple trees.