As a new type of semi-active controller, magnetorheological (MR) brake has been widely used in various braking occasions. In this paper, the working principle of the MR brake was described, and the improvement of the typical MR brake structure was analyzed in order to solve the problems of small braking torque and heat dissipation during operation. At the same time, on the basis of structural improvement, some different optimization methods were discussed. Finally, partial applications and future development issues of MR brake were introduced. The relevant analysis and conclusions can provide certain reference for the design of MR brake.