The　conventional　orthogonal　multiple-access-based　downlink　transmission　for　the　differential　chaos　shift　keying　system　with　pulse-position　modulation　(PPM-DCSK)　suffers　from　lower　energy　efficiency　and　data　rate.　To　tackle　this　problem,　a　low-complexity　superposition　coding　PPM-DCSK　(SC-PPM-DCSK)　system　for　downlink　multi-user　chaotic　communication　is　proposed　in　this　paper.　The　proposed　system　exploits　the　superposition　coding　principle　on　the　reference　signal　and　the　information-bearing　signal　to　achieve　multi-user　simultaneous　information　transmission　for　the　downlink　scenario,　thus　significantly　improving　the　energy　efficiency　and　transmission　rate.　Furthermore,　the　analytical　expression　for　the　error　performance　and　the　throughput　of　the　proposed　system　are　precisely　derived　over　additive　white　Gaussian　noise　and　multipath　Rayleigh　fading　channels.　Simulation　results　not　only　verify　the　accuracy　of　the　analytical　method　but　also　illustrate　the　proposed　transmission　scheme　in　achieving　significant　performance　gain　compared　with　the　time-sharing-based　PPM-DCSK　and　multiresolution　DCSK　systems.　Due　to　such　superiority,　the　proposed　SC-PPM-DCSK　system　can　be　deemed　to　be　an　outstanding　scheme　for　downlink　multi-user　short-range　wireless　communications.　©　1967-2012　IEEE.