The invention discloses a preparation method of basic magnesium carbonate. The preparation method comprises the following steps: drawing an ammonium bicarbonate solution into a syringe with a stainless steel needle head and fixing the syringe on a push pump equipped with high-voltage electrostatic equipment; inserting the stainless steel needle head into a reactor, then setting certain voltage onthe stainless steel needle head of the syringe by utilizing the high-voltage electrostatic equipment, simultaneously setting pushing speed of the push pump, and ejecting the ammonium bicarbonate solution into a reactor; simultaneously putting a magnesium nitrate solution into an ultrasonic atomizer, ultrasonically atomizing the magnesium nitrate solution into a magnesium nitrate atomized object, and introducing the magnesium nitrate atomized object into the reactor through carrier gas for reaction; collecting reaction materials, heating up the reaction materials, adding a crystallization auxiliary into the reaction materials, carrying out precipitation and digestion, performing solid-liquid separation, and performing washing and drying to obtain the basic magnesium carbonate. A preparationprocess disclosed by the invention is simple, the procedures are easily controlled, conditions are mild, and realization is easy; the prepared basic magnesium carbonate is high in purity, contained heavy metal ions are extremely few, stacking density is high, and flowability and quality stability are good.