The invention provides a rosa chinensis enzyme and a preparation method thereof. The preparation method comprises the following steps: adopting barley, grains, fruits and vegetables and edible fungusas well as fresh rosa chinensis as main raw materials, firstly cleaning the barley and the grains, air drying, pulping, stirring, adding amylase until the material is completely liquefied, sterilizing, transferring into a fermenting tank, adding glucoamylase and rhizobacterial enzyme, and performing the fermentation; after the fermentation, adding acetic bacteria dry powder to perform the secondary fermentation; adding diced and juiced chaenomeles speciosa, kiwi fruits, shiitake mushroom and rosa chinensis juice into the secondary fermented solution, uniformly stirring the fruit and vegetablejuice and the secondary fermented solution, adding lactobacillus viable dry powder, performing the tertiary fermentation to obtain an enzyme stock solution; and centrifuging the enzyme stock solution,collecting supernatant, filtering, adding rocky candy powder and erythritol, canning, and sterilizing, thus obtaining the rosa chinensis enzyme. The rosa chinensis enzyme adopts the barley, the grains, the fruits and vegetables and the edible fungus as well as the fresh rosa chinensis as main raw materials, and the multilevel fermentation of various strains is used for replacing the traditional combined fermentation, so that the product quality is easy to control, and the time is relatively short.