The　minimum　point　determination　method　of　the　magnetic　energy　surface　has　been　proposed　on　the　basis　of　magnetic　dipole　theory　in　our　study.　This　method　can　effectively　explain　the　behaviors　that　the　polydisperse　magnetorheological　fluids　(MRFs)　can　form　more　complex　chain-like　structures　and　the　magnetic　energy　of　the　particle　system　will　decrease　with　the　formation　of　the　aggregations.　The　minimum　points　on　the　magnetic　energy　surface　of　two-particle　and　three-particle　system　are　observed,　and　several　kinds　of　stable　microstructures　are　obtained　by　analyzing　these　points.　Finally,　both　the　stability　and　evolution　mechanism　of　these　microstructures　have　been　explored　based　on　the　concept　of　the　magnetic　energy　barrier.　The　results　demonstrate　that　a　minimum　point　on　the　magnetic　energy　surface　of　the　particle　system　corresponds　to　a　type　of　stable　microstructure,　and　the　migrations　between　the　minimum　points　in　the　systematic　magnetic　energy　phase　space　can　be　accounted　for　the　mutual　evolutions　of　these　stable　microstructures.　The　microstructural　stability　depends　on　the　magnetic　energy　barrier　height.　For　this　reason,　the　microstructural　evolution　is　more　likely　to　appear　when　the　barrier　height　is　relatively　low.　In　the　case　of　sufficient　perturbation,　the　particle　system　always　evolves　into　the　state　with　lower　magnetic　energy.　©　1965-2012　IEEE.