The positive polarity Marx nanosecond pulse power supply was designed independently. The electron excitation temperature and electron density of argon discharge in a vacuum were measured and calculated by emission spectroscopy under different discharge frequencies and voltage amplitudes. Through the double line method to choose the appropriate Ar atomic spectrum, electron excitation temperature between 1 550～3 400 K in the regular polarity pulse power voltage source, and under a specific voltage, electron excitation temperature with the increase of power frequency and rise, in power frequency, electron excitation temperature increase with the increase of the supply voltage as well. The electron density in vacuum volumetric dielectric barrier discharge is measured and calculated according to the Stark broadening principle. The order of magnitude of electron density can reach 1013 m-3. When the power supply voltage is constant, the electron density shows a rising trend with the increase in voltage frequency. When the power supply frequency is constant, the electron density also gradually increases with the increase of power supply voltage.