The invention discloses a polypropylene beta crystal form compounded nucleating agent and a preparation method. The formula comprises the following raw materials in percent by weight: 80-98% of polypropylene, 1-20% of a phosphate, 0.1-1% of a flame retardant, 0.1-1% of a dispersant, 0.1-1% of an antioxidant and 0.1-1% of a catalyst. The compounded nucleating agent comprises polypropylene, the phosphate, the flame retardant, the dispersant, the antioxidant and the catalyst in a specific proportion, so that the compounded nucleating agent has good strength, toughness and thermal stability. In the preparation process, by selecting and weighing raw materials; heating and mixing; separating out crystal; washing; drying and forming; and performing preservation and data comparison, great increaseof toughness of the polypropylene product is effectively guaranteed, i.e., impact-resistant strength is greatly increased; crystallization temperature and crystallization rate of polypropylene are increased, and thermal stability is improved; rigid strength of polypropylene is maintained, i.e., modulus is maintained to be unchanged; and dispersibility of the nucleating agent is improved by compounding.