The invention discloses a preparation method of azithromycin intermediate, in particular to a preparation method of azithromycin intermediate 9- deoxidation-alpha- heterocyclic nitrogen-9a-erythromycin A, belonging to the field of pharmaceutical chemical synthesis. The preparation method comprises the steps of: in acid aqueous solution, under the action of potassium borohydride or sodium borohydride, carrying out reduction reaction on erythromycin A 6, 9-imine ether, adding organic saccharic acid for hydrolysis reaction, and obtaining the 9-deoxidation-alpha-heterocyclic nitrogen-9a-erythromycin A. By adopting the method, the hydrolysis of boric acid ester is thorough, the products of acid degradation are less, the yield is high, the production cost of azithromycin is remarkably reduced, and the industrialized production can be very smoothly carried out.