The work aims to study the ionization modes of glow discharge and filament discharge in radio frequency barrier discharge (rf-DBD) at atmospheric pressure (13.56 MHz) and explore the relationship between gas ionization and time and space during one period (73.7 ns). Argon was used to obtain stable glow discharge while filament discharge was obtained by argon doped with nitrogen. In the experiment, ICCD camera was triggered when current crossed zero forward to capture 36 photos at different time points during one period, and the relationship between intensity and time at different positions in the discharge gap during one period was obtained. In α mode, the generation of electron avalanche took place from cathode to anode both spatially and temporally every half period. In γ mode, there was negative glow, and on the dielectric surface of the cathode electrode, the peak time of the intensity of negative glow was about 13 ns later than that of volume ionization. In filament discharge, the luminescence intensity of plasma was mainly concentrated on the cathode surface. The interaction force between the charges accumulated on the surface of the medium caused the generation of independent small channels. Therefore, in α mode, volume ionization is dominant, while in γ mode, in addition to volume ionization, abundant secondary electrons are generated by the impinging of ions on the cathode surface, occurring later than volume ionization. In filament discharge, the charge on the dielectric surface plays an important role, and the ionization on the surface of the cathode medium is the main form of discharge.