The invention discloses a production process for preparing high-purity dehydroacetic acid by virtue of a melt crystallizer. The production process comprises the following steps: introducing freezing saline water into the bottom of a jacket of the melt crystallizer, enabling the freezing saline water to uniformly flow at the outer wall of the crystallizer in a falling film manner, putting a condensed dehydroacetic acid solution into the melt crystallizer, enabling the condensed dehydroacetic acid solution to flow down at the inner wall of the crystallizer in the falling film manner so as to be gradually cooled and crystallized, gradually growing a uniform crystal layer on a heat exchanging face, and gradually enriching impurities in a mixture solution, wherein the concentration of the uniform crystal layer is higher than that of the mixture solution; regulating the temperature of hot water by utilizing a heat exchanger to carry out partial melting operation, namely a sweating process, on the crystal layer, and partially melting and eliminating low-melting-point impurities included in the crystal layer, so as to further purify crystals. The production process has the advantages that the process is simple, and the structures of devices are compact; by utilizing the falling film manner, the energy is reduced, and meanwhile, the cost and the equipment investment are lowered; the purities of products produced by utilizing the melt crystallizer are high.