The invention discloses whitening cosmetic and a preparation method thereof. A composition of a plurality of plants is taken as a main raw material, and the whitening cosmetic mainly comprises the following components: a rice bran extract, a rhodiola rosea extract, a ginkgo leaf extract, tea polyphenol, a lemon juice concentrated liquor, chitosan, a puerarin extract, konjac powder, a sunflower faceplate extract, a sunflower seed extract, a saponin kernel, hemicelluloses and honey. In addition, the whitening cosmetic also contains the following raw materials: a little of glycerinum, 1,3-propylene glycol, squalane, sodium hyaluronate, carbomer, triethanolamine, triethanolamine, allantoin, nanometer titania, collagen powder, an antibacterial agent, a ferulic acid isooctyl ester and glutathione. The composition can be applied to a whitening formula, has the effects of whitening the skin, moisturizing, resisting bacteria and diminishing inflammation, removing free radicals, inhibiting melanin formation, and inhibiting hallachrome mutase and tyrosinase activity.