Abstract: In order to improve the molding fluidity of fumed silica (FS)/cast polyurethane (PU) system, in the process of preparing prepolymer, the fumed silica (FS) was modified by 2, 4-toluene diisocyanate (TDI) to obtain TDI modified silica (NCO@FS), and TDI modified silica/reinforced pouring polyurethane (NCO@FS/PU) elastomer composite material was prepared by in-situ polymerization. NCO@FS and FS were characterized by fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle testing. The results show that the active hydroxyl groups on the surface of FS react with the —NCO groups of TDI to form urethane groups aminoester group (—NHCOO), which improves the interfacial compatibility and interfacial bonding between silica and casting polyurethane. When the mass fraction of NCO@FS in the composite material is 1.5wt%, the tensile and tearing strengths of the NCO@FS/PU composite material are 57 MPa and 110.5 kN/m, respectively, which are 31.6% and 23.6% higher than that of pure casting PU. The glass transition temperature dropped from 3.4°C to –11.2°C, and the loss factor tanδ dropped from 0.59 to 0.46. TDI modified fumed silica is suitable for preparing silica-reinforced cast polyurethane composites.