Brake friction noise is widespread，which affects the driving comfort of car and causes urban noise pollution. Magnetic field tribology research shows that the magnetic field has a positive effect on the stability of friction and reducing wear. Therefore，the magnetic field can be considered to suppress friction noise. Based on the friction-magnetic composite disc brake and simulated brake test bench，the nonlinear mapping relationships between different magnetic field parameters，brake friction noise，friction and wear behavior are analyzed，and the mechanism of restraining brake friction noise by alternating magnetic field is discussed. The results show that the magnetic field can obviously suppress the generation of brake friction noise and the change of magnetic induction intensity has a more obvious effect on noise reduction；the low frequency magnetic field has a better effect on suppressing noise，however too high the magnetic field frequency may increase the noise. The Magnetic field has the mechanism of stabilizing friction and noise reduction，lubrication and noise reduction，and magnetostriction. The fundamental reason is to improve the interface friction and wear characteristics，then increase the proportion of oxidation wear. The abrasive debris is refined and acts as a solid lubricant. The friction interface tends to be stable to achieve the effect of noise reduction. The research results explain the occurrence rule and suppression mechanism of brake friction noise under the action of magnetic field，which can lay a theoretical foundation for the future use of magnetic field to control brake friction noise pollution.