The invention relates to a dimethyl silicate tribromophenoxy bromine propyl ester compound and a preparation method thereof, in particular to a dimethyl silicate bis (2,4,6-tribromophenoxy bromine propyl) ester compound and a preparation method thereof. A structure of the compound is shown as the specification. The preparation method comprises steps as follows: air in a reactor is replaced with nitrogen gas in the reactor equipped with a stirrer, a thermometer and a condenser tube, 2,4,6-tribromophenyl epoxypropyl ether is dissolved in an organic solvent, 0.5 times mole of dimethyldibromosilane is dropwise added, the mixture reacts for 5-11h at the temperature of 30-60 DEG C after dropping is finished, and dimethyl silicate bis (2,4,6-tribromophenoxy bromine propyl) ester is obtained through purification processing. The flame retardant has high flame-retarded efficiency and good material compatibility, the compound is suitable for serving as the flame retardant for polyvinyl chloride, polyester, epoxy resin, unsaturated polyester resin and the like, further, the production technology is simple, the cost is low, and industrial production is easy to realize.