The invention discloses a preparation method of Cs4PbBr6 perovskite nanocrystals with size and shape controllable, and belongs to the technical field of semiconductor nanomaterial preparation. The method comprises the steps that a caesium carboxylate solution is added into a lead bromide solution protected by N2, reaction is conducted under room temperature to synthesize CsPbBr3 nano clusters, andthermal injection is conducted on the CsPbBr3 nano clusters into the caesium carboxylate solution to obtain the Cs4PbBr6 perovskite nanocrystals. The preparation method has the advantages of simple operation, easy adjustment of the size of products, control of the shape of the products and the like.