The present invention discloses a hybrid inflator of an airbag. The hybrid inflator of the airbag includes a main casing, a central channel, a vent tube, a rupture disc, an inner cover group, an igniter group, a first buffering pad, a second buffering pad and a diffuser. The main casing includes a bottom housing and an upper housing. The central channel is fixed with the bottom housing and passed through the upper housing. A convective hole is disposed on the central channel. The vent tube is covered onto the external central channel and has a throttle bore thereon. The first buffering pad is disposed on a bottom of the inter air chamber. The second buffering pad is disposed in the inner air chamber to separate a space for propellant. The diffuser is correspondingly covered and fixed on the main casing.