Abstract: According to the characteristics of 50-5 000 Hz broadband noise in the main exhaust air duct of coal mill house in a cement plant, a resistive chip muffler composed of porous sound-absorbing material, non-woven fabric and porous plate composite structure is designed. Combined with the theory of porous sound absorbing material DB-Miki model, the principle of sound transmission and reflection as well as the principle of sound-induced circulation flow, the mathematical model of equivalent acoustic impedance in the silencing area of the muffler is established, and then the transmission loss of resistive plate muffler is solved by combining the finite element method and transfer matrix method. The correctness of this method is proved by comparing with the experimental results. On this basis, the volume density and fiber diameter of glass fiber cotton in the resistive chip muffler are optimized. The results show that the glass fiber cotton with the fiber diameter of 10 μm and the volume density of 60 kg·m^-3 has the best noise reduction effect. Finally, an engineering example is given to prove the rationality of the design of resistive plate muffler, which provides a certain reference for solving the noise problem of exhaust duct.