Abstract: The traditional fast algorithm is inefficient at high frequency, and diagonal fast algorithm is not stable at low frequency. In order to solve the problem, the fast multipole expression for the simulation of the noise reduction effect of absorbing sound barrier was derived based on Fast Multipole Boundary Element Method (FMBEM). On this basis, a numerical example of an infinite cylinder was carried out to verify the accuracy of the algorithm, and the results show that the fast multipole algorithm has the same accuracy with the traditional fast algorithm, and can improve the computational efficiency. The sound field of different top structures with sound absorbing materials was analyzed, and the results show that the reasonable top structure can increase the noise reduction effect of the barrier effectively, and the sound absorbing materials are also beneficial to improve the effect of noise reduction.