The invention relates to a method for preparing a flaky calcite calcium carbonate crystal, which comprises the following steps of: according to the substance amount ratio of calcium chloride to sodium carbonate as 1.4-1.8:1, adding boric acid or oxalic acid as a crystal shape control agent accounting for 0.8-4.2 percent of the mass of the sodium carbonate into 0.52-3.96mol/L of sodium carbonate solution, and controlling the solution temperature to be 40-90 DEG C; taking 1.24-6.32mol/L of calcium chloride solution, and controlling the solution temperature to be 40-90 DEG C; dropwise adding thecalcium chloride solution into the sodium carbonate solution, stirring as dropwise adding, then stirring at constant temperature for 0.5-2 hours, settling at room temperature for 12-36 hours, and filtering to obtain precipitates; and repeatedly washing the precipitates with water to be neutral, removing adsorbed chloride ions, then filtering, and carrying out vacuum drying at the temperature of 40-80 DEG C to prepare the flaky calcite calcium carbonate crystal. A product is confirmed as a calcite crystal through X-ray diffraction analysis; and a scanning electron microscope result shows that the crystal is regularly flaky. The method has the advantages of low cost, simple process and regular product appearance.