Preparation method of single-phase calcite

The invention discloses a preparation method of single-phase calcite. A solution with certain mole solubility is prepared from soluble carbonate and soluble calcium salt with deionized water, and carbonate ions and calcium ions have equal mole solubility; the soluble calcium salt solution is slowly added to the soluble carbonate solution with stirring, so that the solutions are uniformly mixed, an ultrasonic amplitude-change pole is directly inserted a reaction vessel containing the uniformly mixed solution to be react with the reaction solution directly, ultrasonic treatment is performed at certain power for a certain period, and the solution reacts under the ultrasonic action; a mixed solution product obtained after ultrasonic treatment is continuously mechanically stirred for a certain period to react continuously and then aged for a certain period, and a reaction precipitate is obtained; the reaction precipitate obtained in step 3 is filtered, washed and dried, and calcite can be obtained. Single-phase ca