Packed bed dielectric barrier discharge (PB-DBD) is extremely popular in plasma catalysis applications, which can significantly improve the selectivity and energy efficiency of the catalytic processes. In order to achieve some complex chemical reactions, it is necessary to mix different materials in practical applications. In this work, based on the two-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) method, the discharge evolution in PB-DBD packed with two mixed dielectrics is numerically simulated to reveal the discharge characteristics. Due to the polarization of dielectric columns, the enhancement of electric field induces streamers at the bottom of the dielectric columns with high electrical permittivity (ε_r). The streamers propagate downward in the voids between the dielectric columns with low ε_r, which finally transitions into volume discharges. Then, a new streamer forms near the upper dielectric plate and propagates downward along the void of the dielectric columns with high ε_r. Moreover, electron density in between the columns with high ε_r is lower than that in between the dielectric columns with low ε_r. In addition, the numbers of e, N₂⁺, O₂⁺ and O₂^- present different profiles versus time. All of e, N₂⁺ and O₂⁺ increase in number before 0.8 ns. After 0.8 ns, the number of electrons decreases with time, while the numbers of N₂⁺ and O₂⁺ keep almost constant. During the whole process, the number of O₂^- keeps increasing versus time. The reason for the different temporal profiles can be analyzed as follows. The sum of electrons deposited on the dielectric and those lost in attachment reaction is greater than the number of electrons generated by ionization reaction, resulting in the declining electron trend. Comparatively, the deposition of N₂⁺ and O₂⁺ on the dielectric almost balances with their generation, leading to the constant numbers of N₂⁺ and O₂⁺. In addition, the variation of averaged electron density (n_e) and averaged electron temperature (T_e) in the voids between the dielectric columns are also analyzed under different experimental parameters. Simulation results indicate that both of them decrease with the increase in pressure or the decrease in voltage amplitude. Moreover, they increase with enlarging dielectric column radius. In addition, n_e increases and then decreases with the increase of N₂ content in the working gas, while T_e monotonically increases. The variations of n_e and T_e in the voids can be explained as follows. With increasing pressure, the increase of collision frequency and the decrease of average free path lead to less energy obtained per unit time by electrons from the electric field, resulting in the decreasing T_e. Moreover, the first Townsend ionization coefficient decreases with a reduction in T_e, resulting in less electrons produced per unit time. Hence, both n_e and T_e decrease with increasing pressure. Additionally, T_e is mainly determined by electric field strength. Therefore, the rising voltage amplitude results in the increase of and T_e. Based on the same reason with pressure, n_ealso increases with increasing voltage amplitude. Consequently, both n_e and T_e increase with increasing voltage amplitude. In addition, the surface area of dielectric columns increases with enlarging dielectric column radius. Therefore, more polarized charges are induced on the inner surface of the dielectric column, inducing a stronger electric field outside. Accordingly, the enlarging dielectric column radius results in the increase of n_e and T_e. Moreover, the variation of n_e with N₂ content is analyzed from the ionization rate, and that of T_e is obtained from analyzing the ionization thresholds of N₂ and O₂.