The invention discloses passivating metal magnesium particles and a passivating method thereof. The passivating metal magnesium particles comprise the following components in percentage by weight: less than or equal to 99% and greater than or equal to 92% of Mg, less than or equal to 0.002% of S, less than or equal to 0.01% of Cu, less than or equal to 0.001% of P and less than or equal to 1.2% and greater than or equal to 0.1% of H2O. The passivating method comprises the following steps: (I), preparing a metal magnesium particle passivator, placing metal magnesium particles in the passivator, and then naturally cooling to room temperature; (II), coating a coating on the surface of the magnesium particles: firstly, coating an organic silicon compound on the surface of the metal magnesium particles, coating magnesium oxide on the surface of the metal magnesium particles, then, coating compound rare earth on the on the surface of the metal magnesium particles, and finally coating graphite powder on the surface of the metal magnesium particles; and (III), sieving the metal magnesium particles cooled to room temperature. The metal magnesium particle passivating layer is uniform in coating, and the storage and use safety is ensured.