Based　on　the　physical　facial　features　available　to　visual　perception,　mouth　features　play　an　essential　role　in　perceiving　and　recognizing　facial　expressions,　but　they　have　not　been　as　widely　studied　as　eye　features.　The　NimStim　set　provides　a　more　extended　and　popularized　version　of　the　basic　expressions　with　open　mouth　and　closed　mouth.　In　this　study,　209　Chinese　college　students　were　recruited　to　identify　and　evaluate　the　feelings　of　seven　facial　expressions　in　the　NimStim,　and　we　explored　the　influence　of　open　mouth　on　gender　and　cultural　differences.　The　results　were　as　follows:　(1)　The　open　mouth　did　not　always　correspond　to　a　higher　recognition　rate.　The　neutral　and　sad　expressions　had　a　higher　correct　rate　with　the　mouth　closed,　and　the　happy　expression　had　a　higher　correct　rate　with　the　mouth　slightly　open.　(2)　In　addition　to　neutral　expressions,　females　showed　an　advantage　in　recognizing　emotional　expressions.　The　female　advantage　in　recognizing　sad　expressions　was　more　prominent　in　the　closed-mouth,　and　in　recognizing　fear　(open　mouth)　was　more　prominent　when　the　actor　was　male.　Our　results　advanced　the　role　of　mouth　opening　and　closing　in　facial　expression　perception.　We　also　revealed　that　the　observer’s　gender　affects　the　facial　expression　perception　in　Chinese　culture.　©　2022,　The　Author(s),　under　exclusive　licence　to　Springer　Science+Business　Media,　LLC,　part　of　Springer　Nature.