Automobile auxiliary brake, also known as retarder, is the key equipment to ensure the safety of automobile driving. Its operating quality which is guaranteed by a perfect test system and good test equipment has always been playing an important role. Studies on the test system of miniature vehicle-mounted retarder should be carried out, in order to make it easier to simulate its actual usage and environmental conditions, and also make it more authentic to reflect the properties of magnetorheological fluid retarder. In this way, the research and development level of magnetorheological retarder can be improved, the development cycle can be shortened which leads to the enhancement of brake technology; the test technique of the the magnetorheological retarder and the test level of test bed can also be improved which has a very vital significance to the research and the quality assurance of magnetorheological retarder products and the development of the vehicle braking performance.