Dielectric barrier discharge system (DBD) is a typical nonlinear gas discharge system, which not only has many applications in the industrial production such as low temperature plasma production and luminescence, but also has attracted widespread attention for its physical phenomenon such as non-linear phenomenon and self-organization phenomenon. In order to study the influence of gap distance and gas components on plasma parameters of discharge filaments in DBD system, a discharge cell is redesigned to ensure the other experiment conditions are the same. The discharge cell of this experiment is a flat multiplicate gas gap, which is composed of three thickness of 1.2 mm square glass frames with the discharge area side length as 40, 30 and 20 mm respectively. The multiplicate gas gap is placed in a vacuum chamber with adjustable gas composition and pressure, and three discharge filaments can be generated whose discharge gap distance is 1.2, 2.4 and 3.6 mm respectively. The instantaneous photos taken by high speed video camera indicate that the discharge types of three filaments are all streamer discharge. Arranging the optical path on the line perpendicular to the plane of gap, the focus lens is used to obtain a clear image, and optical fiber probe is moved to achieve spatial resolution acquisition data. The emission spectra of the N2 second positive band (C3Πu→B3Πu) of the three filaments are collected in the experiment by spectrograph. The molecule vibration temperatures are calculated based on emission intensity; based on the relative intensity of the N+2 line at 391.4 nm and the N2 line at 394.1 nm, the electron average energy of the three kinds filaments are investigated. The changing trends of molecular vibration temperature and electron average energy are obtained by changing the Ar content. The results show that, with the increase of Ar content in the 0%~60% range, the molecule vibration temperatures show a trend from rise to drop; The overall trend is that the thinner the thickness of the discharge area, the higher the molecule vibration temperature of the filament in same Ar content. The molecule vibration temperature of the filament in 1.2 mm thick gap is the highest, the second in 2.4 mm thick gap, that in 3.6 mm thick gap is the lowest; As Ar content increases, the electron average energy increases and then decreases; the thinner the thickness of the discharge area, the higher the electron average energy of the filament in same Ar content. The electron average energy of the filament in 1.2 mm air gap thickness is highest, the second in the 2.4 mm gap thickness and the electron average energy of in the 3.6 mm gap thickness is lowest. This paper has an important reference significance for studying plasma parameters and industrial production in DBD system.