In　order　to　conserve　battery　power　in　wireless　sensor　networks,　some　sensor　nodes　may　be　put　into　the　sleep　state　while　other　sensor　nodes　remain　active　for　the　sensing　and　communication　tasks.　However,　determining　which　of　the　sensor　nodes　should　be　put　into　the　sleep　state　is　non-trivial.　In　this　paper,　an　Energy-balanced　Sleep　Scheduling　scheme　based　on　Particle　Swarm　Optimization　(EBSS-PSO)　in　the　context　of　cluster-based　sensor　networks　is　proposed.　The　scheme　aims　to　balance　the　energy　load　of　the　sensing　and　communication　tasks　among　all　the　nodes　in　the　cluster　while　provide　adequate　sensing　coverage　area　and　reduce　the　overlapping　area.　Analytical　and　simulation　results　are　presented　to　evaluate　the　proposed　EBSS-PSO　scheme.　It　is　shown　that　the　EBSS-PSO　scheme　can　extends　the　cluster＇s　overall　network　lifetime　and　reduce　the　overlapping　area　effectively　while　maintaining　a　similar　sensing　coverage　compared　with　three　related　sleep　scheduling　schemes,　the　Randomized　Scheduling　(RS)　scheme,　the　Neighbor-based　Scheduling(NS)　scheme　and　the　Energy-Neighbor-based　Scheduling　(ENS)　scheme.