The invention relates to a plant herbal beverage and a preparation method thereof, and belongs to the technical field of food beverage. The beverage is prepared from the following raw materials: haw flakes, grosvener siraitia, cassia seed, malt, dark plum, honey, white granulated sugar, concentrated apple juice, stabilizing agent and water. The preparation method comprises the following steps of:dipping and boiling the plant raw materials, performing vacuum concentration, clearing, performing enzymolysis, boiling, blending, filtering, degassing, performing ultrahigh-temperature instantaneoussterilization, filling, and thus obtaining the beverage. The plant herbal beverage is sour, sweat and refreshing, and has coordinated faint scent brought by various natural plants; the throat feels comfortable after the beverage is drunk; the beverage is clear and amber, and has uniform impression in the whole quality guarantee period; and moreover, the preparation method is convenient for industrialized production, and the production cost of the beverage is low.