Plasma produced through dielectric barrier discharge can react with hydrocarbon molecules in the fuel by collision cracking reaction, causing fuel molecules to be decomposed into hydrogen and small molecule hydrocarbons that are more prone to detonate, which will improve the ignition properties of the continuous rotating detonation engine with liquid fuel. In this paper, the spectral test of volume dielectric barrier discharge (DBD) was carried out in vacuum chamber in order to analyze how the electron excitation temperature and electron density of volume DBD change with the applied voltage under atmospheric pressure argon. In addition, the electron excitation temperature of filamentous discharge was calculated by the Boltzmann slope method, and the electron density was calculated by Stark broadening method. It was found that all of the emission lines arose from electronically excited argon atoms 4p-4s transitions. The intensities of the lines increased with the increase of the applied voltage and had a linear relationship with the voltage basically. For the atmospheric filamentous discharge, the load voltage has no obvious effect on the electron excitation temperature and the electron density. When the applied voltage is in the range of 12.5～14.5 kV, the electron excitation temperature is stabilized around 3 400 K, and the electron density is on the order of 1025 m-3.