A microplasma-generating device was developed by using needle-plate electrode discharge with the incorporation a Pt/carbon nanotube (CNT) nanocomposite-decorated FTO electrode. When an alternating current voltage of 1.32 kV and a low power consumption of 13 W in nitrogen (N2) carrier gas are applied, the system can be applied to detect methane at room temperature. The main characteristic lines were assigned to CH, C2 and Hα during the discharge process of CH4 at room temperature.The emission intensity of C2 at 516 nm is linear with the concentration of CH4 from 0.5% to 4.0% (φ), and the detection limit (S/N=3) is 0.19% (φ). The emission intensity of Hα at 656 nm is linear with the concentration of CH4 from 0.1% to　3.0%（φ）with the detection limit (S/N=3) is 0.03% (φ). The relative standard deviation (RSD) is less than 2% from 11 repetitive analyses using 3.2% CH4. The Pt/CNT nanocomposite-modified FTO electrode exhibited enhanced sensing performance with precise, repeatability and linear correlation compared with that of the pure MWNT/FTO electrode and bare FTO electrode. When CH4 were discharged in air, the emission spectra of CH4 was different from that in N2. It was found that C2 peak was disappeared and the Hα intensity was also liner to the concentration of CH4 in the range of 0.5%～4%. The established system exhibited advantages with small size, simple fabrication and operation at room temperature compared to other detection system.