The invention relates to the field of agricultural technology and particularly relates to a grafting method of mature theobroma cacao. The method comprises the following steps: cutting a vertical long notch just reaching the xylem in depth in the stock trunk, cutting off the middle stock pieces, peeling off the phloem of the stock pieces at the two ends of the notch, and connecting one ends of the stock pieces at the two ends of the notch with the stock; longitudinally cutting off the phloem from one side of the pre-grafted scion without axillary bud, and exposing the longitudinal cutting surface to obtain a scion; embedding the scion into the notch while enabling the longitudinal cutting surface to match the cambium of the stock; covering the two ends of the scion with the stock pieces at the two ends of the notch; fixing the stock pieces and the scion and wrapping with a plastic film; after the scion survives, removing the plastic film; after the scion and the stock xylem heal, removing the materials for fixing; and when the new branch of the scion grows to 80-100cm long, sawing off the mature stock at a position 40-60cm above the grafting position. In the invention, the exposure surface of the scion wound is reduced, the scion-stock combination is tight, and the grafting survival rate is remarkably increased.