The invention relates to a method for preparing a nano-calcium carbonate whisker/hexagonal boron nitride nanocomposite material. The method comprises stripping hexagonal boron nitride through a simpleultrasonic method, adding the stripped precursor into a calcium chloride solution and synthesizing the nano-calcium carbonate whisker/hexagonal boron nitride nanocomposite material through a simple solution method. The method is simple and safe, realizes a low cost, needs a low temperature and can synthesize calcium carbonate whisker having diameters of about 50nm and good overall uniformity. Thenano-calcium carbonate whisker in the nano-calcium carbonate whisker/hexagonal boron nitride nanocomposite material has a length-diameter ratio of 25-50 satisfying the industrial application requirement. The hexagonal boron nitride has strong oxidation resistance, high temperature resistance and good mechanical properties. The material performances are further improved in application.