The invention belongs to the technical field of biological control, particularly relates to disinfection liquid for rejuvenation and greening of fruit trees and a preparation method of the disinfection liquid. The disinfection liquid is prepared from raw materials: by weight, 10-15% of urea, 5-10% of monopotassium phosphate, 15-20% of saccharose, 10-12% of ferrous sulfate, 3-5% of sodium borate, 2-4% of EDTA chelated zinc, 0.01-0.02% of benzoic acid, 20-40% of walnut green seedcase extract liquid, 0.5-1% of concentrated sulfuric acid, 0.5-1% of absolute ethyl alcohol and the balance being distilled water. The disinfection liquid can improve nutrition condition of the fruit tree, improve symptom iron-deficiency, improve stress resistance of fruit trees, effectively prevent diseases such asring rot, decay, alternaria leaf spot of fruit trees, and achieve rejuvenation of tree bodies and improve yield and income.