The　wall-slip　effect　is　observed　in　areas　with　magnetorheological　fluids　(MRFs).　A　slip　layer　is　formed,　which　reduces　the　friction　between　the　solid　particles　and　working　surface　that　causes　relative　movement　of　the　particles.　This　leads　to　errors　in　the　measurement　of　rheological　parameters　and　an　inaccurate　braking　torque　model.　Thus,　here,　a　rheometer　with　a　sandpaper　on　the　rotor　is　used　to　change　the　working　surface　roughness　to　analyze　the　wall-slip　effect　of　the　MRFs.　Based　on　the　experimental　results,　the　influence　patterns　of　wall-slip　effect　on　fluid　viscosity　and　yield　stress　are　obtained.　Furthermore,　a　MRF　model　is　established　that　considers　wall-slip　effect,　which　is　different　from　the　conventional　models.　The　model　is　employed　to　establish　a　magnetorheological　(MR)　braking　torque　model.　To　verify　the　braking　torque　model,　a　prototype　was　manufactured,　and　its　mechanical　properties　were　tested.　When　compared　with　a　smooth　rotor,　the　braking　torque　of　MR　brakes　with　rectangular　grooves　is　increased.　This　confirms　the　existence　of　the　wall-slip　effect　and　shows　that　the　wall-slip　effect　of　MRF　can　be　effectively　suppressed　by　incorporating　grooves　on　the　rotor　surface.