The invention provides bromelain whitening lotion and a preparation method thereof. The lotion is prepared from the following components in parts by weight: 0.5-1 part of bromelain, 2-10 parts of hyaluronic acid, 50-70 parts of humectant, 2-20 parts of carbomer, 10-20 parts of polyoxyethylene sorbitan monolaurate, 2-20 parts of n-hexyl glucoside, 5-20 parts of triethanolamine, 2-10 parts of oleic alcohol polyoxyethylene ether, 1-2 parts of preservative, 10-20 parts of herbal extract, 5-20 parts of antioxidant and 840-880 parts of deionized water. The preparation method comprises the steps of preparing bromelain, preparing a base solution, preparing an emulsion and compounding. The lotion is prepared by using natural substances as whitening active ingredients, has the advantages of light and thin texture and good absorption, and cannot easily cause skin allergy.