Embodiments of the present disclosure relate to a power tool assembly, including a tool body and a battery pack. The battery pack includes: an accommodated cell unit, a battery pack electrode base, a mounting cavity, and a locking apparatus. At least one of a power tool and the battery pack is configured with a plug socket seal member. The battery pack further includes an upper-lower housing body seal member disposed at a connection between an upper housing body and a lower housing body. When the upper housing body is coupled to the lower housing body, the upper-lower housing body seal member blocks communication between the outside and the mounting cavity. The locking apparatus is mounted on a battery pack housing, and the locking apparatus is isolated outside the mounting cavity.