The invention provides an aluminum material stabilizing device of a plate bending machine, and relates to the field of profile processing. The aluminum material stabilizing device comprises a stabilizing bracket, and the stabilizing bracket comprises a touchdown part used for placement on ground, and a lifting frame part used for clamping aluminum materials; the lifting frame part comprises a horizontal lifting seat and an expansion clamp, and the horizontal lifting seat is provided with a horizontal moving groove and a vertical clamping groove; the expansion clamp comprises a horizontal moving rod and a limit straight rod, and the horizontal moving rod is a rectangular straight rod extending horizontally; the limit straight rod is a straight rod penetrating the vertical clamping groove from the upper surface of the horizontal moving rod and extending vertically upwards; the horizontal moving groove is further provided with spacing bulges, and the spacing bulges are arc-shaped convex particles which extend upwards from the upper surface of the horizontal moving groove and arranged at intervals; aluminum plates which need to enter the plate bending machine are stably limited, and the entry attitude and status of the aluminum plates are ensured; and the situation that the machined aluminum plates fall randomly and consequently are deformed is avoided.