The invention provides a polyurethane resin composition and a preparation method thereof, wherein the polyurethane resin composition comprises a polyol, diphenylmethane diisocyanate, an organic silicon polymer, a catalyst, a chain extender, a stabilizer and a flame retardant, wherein the organic silicon polymer accounts for 5-10% of the mass of the composition. According to the present invention, the polyurethane resin composition has advantages of good sound absorption and noise reduction performance, excellent electrical insulation performance, excellent high-low temperature resistance and excellent flame retardancy; the traditional polyurethane material has the low sound absorption coefficient of about 0.74 while the sound absorption coefficient of the polyurethane resin composition of the present invention is 0.82-0.87, such that the sound absorption coefficient is substantially improved, and the noise pollution can be significantly reduced; by adding the boronized organic silicon polymer, on the premise of the maintaining of good electrical insulation performance and good flame retardancy, the sound absorption and noise reduction performance of the polyurethane system can be significantly improved; and the obtained polyurethane resin composition can be used as the sound absorption and noise reduction in the direct current converter valve saturable reactor device.