How　to　design　an　energy　efficient　routing　algorithm　is　a　hot　topic　in　the　research　of　wireless　sensor　networks.　In　this　paper,　based　on　the　analysis　of　some　typical　cluster-based　routing　algorithms,　a　novel　cluster-based　energy　efficient　routing　algorithm　is　proposed　to　solve　the　hot　spot　problem　involved　in　inter-cluster　routing　and　optimize　network　lifetime.　Clusters　are　formed　by　local　competition　and　the　role　of　cluster　head　is　rotated　among　sensor　nodes　periodically　to　balance　energy　consumption　in　WSN.　Furthermore,　Particle　Swarm　Optimization　algorithm　is　utilized　to　search　optimal　inter-cluster　routing　path　for　the　optimization　of　network　lifetime.　Simulation　results　prove　the　effectiveness　of　the　routing　algorithm　proposed　in　this　paper.　©　2010　IEEE.