The invention discloses a plant whitening lotion and a preparation method thereof. The lotion comprises main components as follows: nicotinamide, glycerin, butanediol, glycerol polyether-26, a centella asiatica extract, a opuntia streptacantha stem extract, cassava starch, trehalose, sodium hyaluronate, a tremella extract, tremella polysaccharide, a pearl extract, a poria cocos extract, a snow lotus herb extract, a ginseng root extract, a herba cistanches extract, a ganoderma lucidum extract, p-hydroxyacetophenone and hexanediol. The preparation method of the plant whitening lotion comprises following steps: component mixtures A and B are prepared from part of components, the mixtures A and B are mixed, emulsified, stirred and cooled, the p-hydroxyacetophenone, the hexanediol, the centellaasiatica extract, the opuntia streptacantha stem extract, the cassava starch, the trehalose, the tremella extract, the tremella polysaccharide, the pearl extract, the poria extract, the snow lotus herb extract, the ginseng root extract, the herba cistanches extract and the ganoderma lucidum extract are added, after uniform stirring and defoaming, the materials can be discharged. The plant whitening lotion has significant whitening effects.