The invention relates to a device used for testing 
magneto-rheological 
fluid shear yield stress. The testing device mainly comprises an adjustable uniform 
magnetic field generating device, a steel 
barrel, a rotary shaft, a seal ring cover plate, a support, a motor, a 
torque sensor, a Hall piece, a 
data demodulation single-
chip microcomputer and a testing display instrument. The testing device has the advantages that the 
magnetic field generating device can generate a large adjustable uniform 
magnetic field; wall face sliding can be prevented from occurring to 
magneto-rheological fluid under the condition that the magnetic field exists; a testing and displaying device enables weak 
voltage difference signals to be output onto the testing display instrument accurately in real time through a 
torque sensor, the PWM theory, a 
signal amplifying circuit and A / D conversion; a low-reluctance 
closed loop is formed on the outer side of a close-wound coil through industrial pure iron, and a coil fixing frame on the inner side of the close-wound coil is made of nylon materials so that more magnetic lines can pass through the 
magneto-rheological fluid. The magneto-rheological fluid is arranged in the center of the magnetic field generating device, so that the magnetic induction strength generated by the detected magneto-rheological fluid is distributed evenly and perpendicularly.