The invention discloses a polypropylene composite material available for chemical micro-foaming and a preparation method thereof. The polypropylene composite material is uniformly mixed with a composite foaming agent, and the polypropylene composite material is formed by adopting secondary mold-opening injection molding, wherein the polypropylene composite material is prepared from the following components in parts by weight: 65 to 85 parts of polypropylene, 10 to 20 parts of active calcium silicate, 10 to 15 parts of a flexibilizer, 0.4 to 0.8 part of a modifier, 0.2 to 0.4 part of an antioxidant ,0.5 to 1 part of a lubricating agent, 0.5 to 1 part of a cross-linking agent, 0.2 to 0.5 part of a cross-linking assistant and 0 to 3 parts of other assistants. The surface of the active calcium silicate is coated by adopting synergy of the cross-linking assistant and the surface active agent, the interfacial force with resin is strengthened, the dispersion is more uniform, and simultaneously a polypropylene cross-liking reaction is triggered through the cross-linking agent to form a network-shaped structure, so that the melt strength of the composite system is improved, and the composite material has excellent foaming performance; and the composite material has the characteristics of wide source of raw materials, low cost, small density, high dimensional stability, excellent mechanical performance, heat insulation, sound insulation and noise reduction.