Abstract: In methane-hydrogen and methane-helium systems, optical emission spectroscopy(OES) is used to diagnose the active species emission in the low-pressure methane plasma by spiral wave discharge. In experiments, the main species as H(Ha, Hb, Hg) and CH have been identified in the two systems. In CH4/He system, the intensities of these active species first increased and then decreased with the increase of the input RF power, and as the gas pressure increased, the intensity of the CH radical decreased, the intensities of Ha, Hb and Hg species initially increased and then decreased. In CH4/H2 system, the relative intensities of Ha, Hb, Hg and CH radicals increased with the increase of the input RF power, and the relative intensities of all these radicals initially increased and then decreased wit