The invention relates to a preparation method of a natural composite food color fixative, belonging to the technical field of food processing. The method comprises the following steps: soaking fresh blueberries with an ethanol solution, cooling and grinding into powder; uniformly mixing the powder with the filtrate collected after cooling, microwave oscillation and centrifugation of fresh roxburgh rose pulp soaked with metaphosphoric acid; fermenting in a fermentation tank, and adding a nutrient solution into the fermentation tank; after the fermentation, collecting the fermented liquid and mixing with ethanol; performing reflux and centrifugal separation; and collecting the supernate and mixing with substances such as sodium chloride. The beneficial effects of the invention are as follows: the prepared color fixative is natural without harm; the original color of the products can be maintained while browning can be reduced during processing; and meanwhile, the preparation steps are simple, and the cost is low.