The invention discloses a preparation method of foamed polypropylene beads. The method comprises the following steps that 1, polypropylene resin, an active filler and auxiliaries are added into a high-speed mixing machine and mixed to be uniform at the temperature of 10-20 DEG C, and a polypropylene foaming material is obtained; 2, the polypropylene foaming material is added into a triple-screw extruder, plastification and mixing are conducted, a supercritical fluid is injected, the mouth mold pressure is controlled to be 5-25 MPa, the mouth mold temperature is 110-160 DEG C, instant pressure release is conducted through a mouth mold, foaming is conducted, and super-fine hole foamed polypropylene is obtained; 3, super-fine hole foamed polypropylene is subjected to mold surface water-ring hot-cutting granulation, drying and sieving, and the foamed polypropylene beads are obtained. The method is low in production cost, high in capacity, safe and environmentally friendly, no foaming agent decomposed residue exists in the prepared foamed polypropylene beads, secondary foaming can be conducted, the foaming ratio can be adjusted, the rebound resilience of a finished product is high, decomposing and recycling are easy, and the foamed polypropylene beads can be widely used in the fields of plastic packaging, transportation industry, military aerospace, office supplies and the like.