The invention relates to a high impact resistant polyformaldehyde compound and a preparation method thereof. The compound is prepared from the following components in part by weight: 80 to 99 parts of polyformaldehyde resin, more than 0 and less than or equal to 20 parts of low-density polyethylene grafted nano silicon dioxide, 0.2 to 1 part of antioxidant and 0.2 to 1 part of stabilizer. The compound solves the problems of decline of rigidity, heat resistance and abrasion resistance in a common elastomer toughened and modified POM compound. The obtained polyformaldehyde compound has the advantages of high strength, high rigidity, impact resistance, abrasion resistance, self lubrication, thermal stability, good liquidity, easy processing and molding and the like, is quite suitable for manufacturing abrasion-resistant parts of automobiles, food machinery, papermaking, agricultural machinery and the like, and has broad application prospect.