The discharge of DBD in unburned gaseous fuel or the combustible mixture will produce a lot of active free radicals, which can promote combustion and improve the combustion characteristics of fuel. In this paper, the effect of DBD excited methane on gliding arc flame is studied by using the key active particles (CH and OH) produced by DBD to enhance combustion. Therefore, a self-designed DBD-Gliding arc dual-mode plasma exciter is used to excite argon, methane and air mixture by using a coaxial Dielectric barrier discharge structure. The argon, methane and air mixture after excitation is fed into the gliding arc end for ignition. The volume flow ratio of argon to Air-methane in the inlet passage can reach Ar∶(CH₄+Air)=1∶30 by adjusting the Airflow rate to 4.76 L·min^-1 and adding methane to 0.5 L·min^-1, the mixture of argon, methane and methane can be discharged and burned uniformly and stably when the equivalent ratio of chemical combustion isϕ=1. The discharge voltage in the DBD segment varies from 15 to 20 kV, and the discharge frequency varies from 6 to 10 kHz. The voltage and frequency in the gliding arc discharge segment remain constant at 4 kV and 10 kHz, respectively, the type and spectrum intensity of free radicals in gliding arc flame were measured by a high-speed optical fiber spectrometer, and the effect of methane excited by discharge parameters on free radicals (CH and OH) in-flame was analyzed. The results show that the increase of DBD voltage and frequency can promote the coupling reaction in the flame and can effectively increase the content of active particles in the methane gliding arc flame. The OH group and CH group play an important role in the combustion chain reaction. The OH and CH groups in the flame increase with the increase of DBD discharge voltage and frequency. After DBD discharge, the spectrum intensity of the active particles increases, and the characteristic spectrum is more obvious than that of a single-mode. After the methane is excited by DBD, the flame composition changes, and the methane combustion reaction at the exit of the gliding arc is sufficient. The higher the flame temperature, the more likely it to produce an OH group. Compared with the single-mode GAD, the Double mode discharge can promote the chain chemical reaction process and fuel combustion.