In　order　to　study　the　influences　of　sealing　gap　on　the　seal　of　magnetorheological　fluids　(MRF),　the　quasi-static　tensile　tests　along　the　direction　of　magnetic　field　have　been　carried　out　by　using　a　commercial　plate-plate　rheometer.　Based　on　the　experimental　results,　the　relationships　among　the　height　of　sealing　gap,　magnetic　field　intensity,　particle　concentration　and　the　sealing　properties　of　MRF　are　discussed.　The　analysis　results　show　that　the　sealing　performances　of　MRF　will　deteriorate　with　the　increase　of　sealing　gap,　especially　when　the　MRF　is　exposed　to　a　strong　magnetic　field.　This　is　probably　due　to　the　fact　that　the　material　properties　of　MRF　become　more　similar　to　the　solid　with　the　rise　of　magnetic　field,　which　makes　the　sealing　layer　more　brittle　and　prone　to　leakage.　The　tensile　process　in　low　magnetic　field　can　be　divided　into　the　forming　of　seal　region,　stable　seal,　leak　and　balanced-pressure　four　stages,　in　which　the　stable　seal　stage　shows　that　the　MRF　has　certain　self-healing　ability　of　seal.　Furthermore,　both　the　initial　compressive　strength　and　the　sealing　stability　of　MRF　can　be　significantly　improved　by　increasing　the　volume　fraction　of　MRF.　Finally,　a　theoretical　model　for　calculating　the　burst　pressure　of　MRF　seal　is　proposed　according　to　the　theory　of　magnetic　dipole.　The　description　of　the　relationship　between　various　influencing　factors　and　the　sealing　characteristics　of　MRF　by　this　model　is　consistent　with　the　experimental　results,　which　indicates　that　the　model　has　favorable　instructing　value　in　the　practical　engineering　application.