The invention discloses a radial extrusion type magnetorheological fluid brake, and belongs to the field of hydraulic resistance brakes. On the basis of an existing device, a right guiding magnetic brake outer shell, a pressurization device, a coil fixing ring, pressurization channels, a right magnet exciting coil and a separation magnet ring are added to the brake, wherein the right guiding magnetic brake outer shell is arranged on the right of a left guiding magnetic brake outer shell, a gap is reserved between the right guiding magnetic brake outer shell and the left guiding magnetic brake outer shell, and the pressurization device is arranged on the outer circumference of the right guiding magnetic brake outer shell; a magnetorheological fluid gap is formed between a driving shaft and the right guiding magnetic brake outer shell, the other magnetorheological fluid gap is formed between the driving shaft and the left guiding magnetic brake outer shell, and a left magnet exciting coil, the right magnet exciting coil and the separation magnet ring are arranged in the gap formed between the right guiding magnetic brake outer shell and the left guiding magnetic brake outer shell; and the left magnet exciting coil and the right magnet exciting coil are fixed through the coil fixing ring, the pressurization channels are respectively arranged on the right guiding magnetic brake outer shell, the coil fixing ring and the separation magnet ring. The radial extrusion type magnetorheological fluid brake is simple in assembling and compact in structure, provides large braking torque, meanwhile enhances device reliability, and reduces energy consumption.