Sound absorption is an effective noise reduction measure, and sound absorption materials are widely used in noise control of various mechanical equipment and their components. By testing the noise of a 1.7kW variable frequency generator set, it is found that the generator set had the problem of poor noise reduction effect of the original sound absorbing material. The noise of 25%～75% load was only reduced by 0.1～0.4 dB(A). Under no-load condition, the noise of the generator set had increased by 1.1 dB(A) instead. The comparative test was carried out by replacing four kinds of sound absorbing materials with different parameters, and it is found that the sound absorbing material with a material of polyurethane, a density of 35kg/m3, and a thickness of 10mm had the best noise reduction effect. Compared with the original state, the noise under the four loads (no load, 25% load, 50% load and 75% load) had been reduced by 1.1 , 0.8, 0.2, 0.6 dB(A), the noise of the generator set has been further improved. The noise reduction analysis results of sound absorbing materials could provide ideas for noise control of generator sets.