An　improved　LEACH　for　heterogeneous　wireless　sensor　networks　is　proposed.　Nodes　are　distributed　in　a　sensing　area　that　is　divided　into　a　number　of　same　equilateral　hexagons.　Heterogeneous　nodes　act　as　the　cluster　heads　and　ordinary　nodes　act　as　those　cluster　sensors　in　all　clusters.　The　structure　of　WSNs　is　a　two-layer　structure.　The　upper　layer　consists　of　all　cluster　heads　and　the　lower　layer　consists　of　all　ordinary　sensors　managed　by　their　corresponding　cluster　heads.　The　cluster　heads　and　the　ordinary　sensors　establish　their　pairwise　keys　respectively　through　utilizing　different　methods.　The　arithmetic　balances　energy　expense　among　all　kinds　of　nodes,　saves　the　node　energy,　and　prolongs　the　life　of　wireless　sensor　networks.　Additionally,　Analysis　demonstrates　that　the　security　of　wireless　sensor　networks　has　been　improved　obviously　even　with　some　heterogeneous　nodes.　©　Copyright.