The invention relates to a method for preparing a polypropylene composite. The method is characterized in that the polypropylene composite is prepared from polypropylene, a compatibilizer, glass fibers, a nucleating agent and an anti-oxidant according to a two-step process. The method comprises the following steps: the nucleating agent is utilized to induce crystal transfer of polypropylene; the glass fibers are compounded with polypropylene subjected to crystal transfer for further enhancement. Therefore, the problem that according to a traditional method in which polypropylene is directly mixed with a nucleating agent and fibers, the polypropylene crystallization behavior regulation and control functions of the nucleating agent cannot be effectively played due to introduction of the glass fibers serving as external impurities is solved. According to the method provided by the invention, regulation and control of the nucleating agent and enhancement of the glass fibers are effectively combined together to improve the combination property of the polypropylene composite, so that the polypropylene composite prepared by the method is not only excellent in comprehensive mechanical property but also high in thermal stability. Meanwhile, the raw materials (the glass fibers) are low in price and easily accessible, and a twin-screw extrusion process is simple and low in cost, so that large-scale production and application can be conveniently realized.