Considering　all　the　harmonic　components　for　the　arm　current,　this　paper　proposes　a　new　steady-state　operation　characteristic　analysis　method　for　the　modular　multilevel　converter(MMC).　Based　on　the　analysis　of　the　coupling　relationship　among　the　internal　electric　variables　of　MMC,　the　general　matrix　equation　of　the　system　is　derived　and　the　analytical　expression　of　the　arm　current,　submodule　capacitor　voltage　and　circulating　current　is　obtained,　and　then　the　operation　law　of　these　variables　is　concluded.　The　calculation　process　is　relatively　simpler　and　the　analysis　results　are　more　accurate　with　this　method.　The　simulation　and　experimental　results　based　on　23-level　MMC　back-to-back　platform　are　compared　to　the　analytical　results,　respectively.　It　verifies　that　the　proposed　method　is　feasible　and　accurate.　©,　2015,　Chinese　Machine　Press.　All　right　reserved.