The invention discloses a preparation method of noni wine. The preparation method is implemented according to the following steps of: (1) cleaning and arranging noni fruits, removing bad and decayed fruits and impurities, then adding SO2 for disinfecting, crushing, conducting self digestion, clarifying and separating; (2) adjusting the components, adding active dry yeast for fermenting, changing barrels, filtering after the fermentation, and ageing; and (3) blending, ageing, bottling and disinfecting to obtain the noni wine. According to the preparation method disclosed by the invention, the endogenesis enzyme contained in the noni fruits is utilized for self digestion of pulps, so that the separation of fruit juice and pomaces is facilitated; due to the addition of sulfur dioxide, the oxidation loss of vitamin C and the like of the noni wine can be avoided, the storage rate of the nutrient contents of the noni wine is increased, and the immune of a human body is enhanced; and secondly, after the noni fruits are fermented, the flavor of the noni product is improved, the prepared wine is pure and mild in taste, is harmonious in sweetness and sourness, and unique in flavor.