Disclosed is a production process for preparing high-purity dehydroacetic acid by using melt crystallization, the process including the following steps : first introducing chilled brine into the bottom of a jacket on the outside of a melt crystallizer, allowing the chilled brine to uniformly flow on an outer wall of the crystallizer in a falling film manner, then putting a condensed dehydroacetic acid solution into the melt crystallizer, and allowing the dehydroacetic acid solution to flow down an inner wall of the crystallizer in a falling film manner and gradually crystallize during cooling, whereby a uniform crystal layer is gradually grown on a heat exchange surface, wherein the concentration of the crystal layer is higher than that of a mixture solution, and impurities are gradually concentrated in the mixture solution; and then, carrying out a partial melting operation on the crystal layer by adding the temperature of hot water by means of a heat exchanger, that is, a sweating process is involved to partially melt and eliminate low-melting-point impurities entrained in the crystal layer, so as to further purify the crystal. The present invention has a simple process, involves a compact equipment structure, and uses a falling film form, thereby resulting in reduced energy, while also reducing costs and equipment investment; and a product produced by using this melt crystallizer has a high purity.