Atmospheric pressure plasma plume generated by pulsed discharge is studied by experimental diagnostics and numerical simulations. It is found that the plasma plume is generated in the rising phase of pulse voltage, in which a plasma bullet propagates toward the ground electrode at a speed on the order of 10⁴ m/s. It is also found that the electric field in the vicinity of the plasma bullet reaches 10⁶ V/m, indicating that the formation of plasma bullet can be attributed to the localized enhanced electric field, which will be enhanced near to the grounded electrode. The spatiotemporal evolution of electron density in the discharge reveals that the residual electron density remains after the plasma bullet has passed through, which explains the tailing phenomenon of plasma bullet. The enhanced electron generation rate at the head of plasma bullet corresponds to the localized enhanced electric field, which explains the generation mechanism of plasma bullet. This study of the characteristics and mechanism of plasma bullet provides a theoretical basis for developing the atmospheric plasma plume generated by pulsed discharge.