Magnetorheological brake (MRB) is a new brake-by-wire device. It consists of rotating disk immersed in a MR fluid and enclosed in an electromagnet, where the yield stress of the fluid varies as a function of the magnetic field applied by the electromagnet. Based on Bingham model, the torque formula of disc-type MRB was presented, and the coupling relationship between its structure and magnetic circuit was analyzed. An optimization design method for the disc-type MRB was proposed based on the simulation analysis of coupling model of structure and magnetic circuit. Maximizing braking torque and minimizing brake weight were taken as optimization objectives, and the multi-objective was converted into single objective by the variable weights. An optimization procedure based on the parameterized finite element analysis of ANSYS integrated with an optimization tool was used to obtain optimal design scheme of MRB. The prototype of MRB was fabricated and tested to evaluate its performance. The experiment bench system of MRB was developed. Experimental and simulation results showed that the designed scheme of MRB can meet the braking torque requirements and the designing demands of magnetic circuit.