The invention relates to a water-based polyglycerol tartaric acid ester compound and a preparation method thereof. The water-based polyglycerol tartaric acid ester compound has both a tartaric acid structure and a polyglycerol structure, not only has good biocompatibility, modificability and biodegradability of tartaric acid ester, but also has a large number of free carboxyl groups and polyhydroxyl structures of polyglycerol, and has excellent properties in the aspects of moisturizing, emulsifying, stabilizing, salt tolerance and the like. The preparation method has the advantages that polyglycerol and epoxy chloropropane react to obtain polyglycerol with epoxy units, then the polyglycerol with the epoxy units reacts with polycarboxylic tartaric acid, so that free carboxyl units can be obtained, more carboxyl groups can be obtained, and therefore the moisture retention property, the emulsifying property and the salt tolerance of a product can be greatly improved, the compound is usedfor skin care products, and meanwhile, the skin is enabled to have good smoothness.