ZnS:Cu,Mn electroluminescent (EL) materials were prepared by two different methods of Cu-doping on the ZnS:Mn particles. The microstructure and value of x in CuxS phase was examined in detail by transmission electron microscopy and selected area electron diffractometry. The coexistence of Cu2+ and Cu+ in CuxS phase was found by X-ray photoelectron spectroscopy and electron spin resonance. Attempts were made to elucidate the role of CuxS phase on the surface and interior of ZnS:Cu,Mn EL device. The coating method brought about a five times higher EL intensity than the conventional method.