The IR emission spectra of methane were measured under DC glow discharge conditions. The distinct difference in time between methane decomposition and C-2 hydrocarbons formation was specially pointed out. C-2 hydrocarbons formed at the end of methane decomposition. The optimum condition for C-2 hydrocarbon formation was studied and the optimum combination between electric current density and methane input quantity was suggested. The appropriate reaction conditions for methane decomposition and C-2 hydrocarbons formation are different, so high yield Of C-2 hydrocarbons will be probably obtained when different conditions are taken.