The invention relates to a halogen-free flame-retardant long glass fiber reinforced polypropylene material, which comprises the following raw materials in percentage by weight: 49 to 88.8 percent of polypropylene, 0.1 to 0.5 percent of thermal stabilizer, 0.1 to 0.5 percent of lubricating agent, 5 to 20 percent of halogen-free flame retardant, 1 to 5 percent of glass fiber compatilizer and 5 to 25 percent of long glass fiber, wherein the polypropylene is high fluidity polypropylene. The invention also relates to a preparation method for the polypropylene material. The preparation method comprises the following steps of: preparing a long glass fiber master batch and a halogen-free flame-retardant master batch, mixing the two master batches uniformly, and thus obtaining the polypropylene material, wherein when the polypropylene material is used, the polypropylene material is directly used for injection molding of parts. The polypropylene material has excellent flame-retardant property and dimensional stability, high mechanical strength, low shrinkage rate and good creep resistance and thermal oxidation resistance, is suitable for injection molding of thin-wall large pieces and automotive part products with complex structures such as automotive engine bottom guard plates, front-end modules, instrument panel frameworks and the like, saves the automobile manufacturing cost, and is environment-friendly.