The invention discloses a preparation method of an enhanced multiphase crystal based on calcite and aragonite. The preparation method mainly solves the problems that in the prior art, a calcium carbonate preparation method is complicated, expensive and not easy to control whiteness. The preparation method comprises the steps of firstly mixing calcium chloride, magnesium chloride, sodium carbonate and sodium hydroxide with deionized water so as to prepare into solutions; then mixing the calcium chloride solution, the sodium carbonate suspension liquid and the sodium hydroxide suspension liquid, heating, and stirring to prepare into a calcite and aragonite multiphase suspension liquid; adding a magnesium chloride water solution into the calcite and aragonite multiphase suspension liquid, and preparing into the enhanced multiphase crystal based on calcite and aragonite; precipitating, cleaning, drying, and grinding to obtain lamellar crystals with the thickness being 0.05 to 0.1 micrometer, the diameter being 0.2 to 4 micrometers and uniform size distribution. According to the preparation method of the enhanced multiphase crystal based on calcite and aragonite provided by the invention, the whiteness of the crystal is improved, the used raw materials are cheap, the process is simple, and the enhanced multiphase crystal can be applied in manufacturing plastics, rubbers, catalysts, medicines, ceramics, papermaking, ink and coatings.