Aiming　at　excessive　users　existing　in　a　pico　base　station　(PBS)　in　the　multi-layer　heterogeneous　networks,　the　resource　allocation　problem　of　maximizing　the　energy　efficiency　of　the　networks　is　investigated　in　this　paper.　By　deploying　a　relay　node　with　energy　harvesting　function,　the　data　of　some　users　in　the　PBS　can　be　transferred　to　an　adjacent　idle　PBS.　The　bandwidth　and　transmitting　power　of　users　and　the　relay　node　are　both　considered　to　formulate　the　resource　allocation　optimization　problem.　The　objective　is　to　maximize　the　energy　efficiency　of　the　whole　heterogeneous　networks　under　the　constraints　of　the　user’s　minimum　data　rate　and　energy　consumption.　The　suboptimal　solution　is　obtained　by　using　the　particle　swarm　optimization　(PSO)　algorithm　and　quantum-behaved　particle　swarm　optimization　(QPSO)　algorithm.　Simulation　results　show　that　the　adopted　methods　have　higher　energy　efficiency　than　the　conventional　fixed　power　and　bandwidth　method.　In　addition,　the　time　complexity　of　the　adopted　methods　is　relatively　low.　©　2021,　Shanghai　Jiao　Tong　University　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.