The invention provides a high-transformational-entropy nano MnO2 particle preparation method. The preparation method includes the step that MnO2 subjected to hydrothermal synthesis is adopted for preparing high-transformational-entropy MnO2 particles under the action of F ions and (NH4)2S2O8. The nano particles prepared according to the method are high in crystallinity, dispersity and transformational entropy. Compared with the prior art, the special nano particle synthesis method has advantages that Mn crystallinity can be adjusted in solution through ion exchange, controllable synthesis of the nano MnO2 particles is realized, and the particles obtained according to the method are higher in transformational entropy than reported MnO2 block materials.