Disc brake squeal is a complicated dynamic problem confronting automobile manufacturer for decades. A squealing disc brake is studied and a closed-loop coupling model with 128 degrees of freedom is established on the basis of Finite Element Method and Modal Synthesis Method. Based on the system model, calculation and analysis are performed to find which structure factors affect squeal phenomenon greatly. At last, it is found that some of the mounting bracket modes dominate the appearance of the squeal. According to that, possibly the structure modification of the bracket is an accessible way to eliminate the brake squeal.