In　order　to　reduce　the　impact　force　of　the　legged　hydraulic-robot　when　it　is　driving　on　the　ground,　a　new　method　based　on　magnetorheological　technology　is　proposed　for　damping　control　of　hydraulic　mechanical　legs　in　this　paper.　Firstly,　the　structure　of　hydraulic-driven　leg　with　magnetorheological　fluid　(MRF)　damper　is　designed,　and　the　magnetic　field　simulation　analysis　of　MRF　damper　is　carried　out　to　verify　the　rationality　of　magnetic　circuit.　Then　the　effects　of　different　damping　ratios　on　the　dynamic　performance　of　valve-controlled　cylinder　system　are　analyzed　by　theoretical　modeling.　Further,　the　co-simulation　modeling　of　MRF　damper　and　valve-controlled　cylinder　is　established　based　on　AMESIM　to　analyze　the　vibration　reduction　effect　under　impact　force.　Finally,　the　experiments　of　the　hydraulic　system　designed　in　this　paper　are　carried　out　under　step　load　and　triangular-wave　load　to　obtain　the　system　output　displacement　and　pressure　under　two　kinds　of　loads.　Compared　with　the　results　without　MRF　damper,　it　is　found　that　the　new　method　can　reduce　the　increase　of　pressure　impact　by　82%　and　almost　eliminate　the　pressure　fluctuation　in　the　high　pressure　chamber　of　hydraulic　cylinder.