Abstract: In order to predict and control wheel/rail impact noise due to wheel flats in fast speed and semi-high speed railway, a model which could simulate wheel/rail impact noise is set up based on the vehicle-track coupled dynamics theory and the sound radiation theory. The acoustics performances of wheel/rail impact noise due to railway wheel flats had been studied with wheel/rail noise simulation software TTINSIM. The results demonstrated that railway wheel flats which cause wheel/rail impact noise are important sources. Wheel/rail impact noise due to wheel flats are focused mainly in frequency domains upon 250Hz. Impact noises due to wheel flats is related to length and quantity of wheel flats and the train speed. The differences of impact noises due to new flats and old flats are 2～3dB(A).