A method for treating rot and dry rot of fruit trees is characterized by including following steps: 1, the preparation stage, wherein disinfection and sterilization are conducted on a special tool, prepared disinfectant is put into a sprinkling can, the 30-fold to 50-fold liquid of prepared agricultural antibiotic 120 liquid and leaf fertilizer liquid are put into a sprayer as nutrient solutions, and lard oil is extracted and purified into liquid; 2, the cleaning stage, wherein liquid spraying is conducted on disease scars of the fruit trees through the disinfectant prepared in the first step, raw barks on the edges of the disease scars are scraped away through the back face of the disinfected special tool after the edges of the disease scars are seen, secondary spraying is conducted through the disinfectant, the middles of the disease scars are then taken out, residual parts are thoroughly removed through the special tool, sterilization is conducted on the cleaned parts through the disinfectant, and spraying sterilization is conducted on tree bodies and the ground through the disinfectant; 3, the maintenance closing stage, wherein the prepared nutrient solutions are sprayed to the disease scars, the disease scars are smeared with lard oil liquid after natural air drying, and smearing is conducted again after solidification. By means of the method, rot and dry rot of the fruit trees can be effectively prevented and controlled, and lesion reoccurring of the fruit trees is prevented.