The invention discloses a common adjustable rain cover. The common adjustable rain cover comprises a rain cover body, wherein the rain cover body is unfolded to form a fan ring; at least one row of radially arranged first through holes is formed on one side of the rain cover body; at least two rows of radially arranged second through holes are formed on the other side of the rain cover body; the at least two rows of second through holes are respectively formed in different circumferential directions; one side of the rain cover body is partially overlapped with the other side; at least one rowof first through holes on one side is coincided and aligned with the second through holes on the other side; and connectors pass through the first through holes and the second through holes for connection and fixing. During the mounting, the upper end of the rain cover is wrapped and laminated with an insulating rod, and rain can flow along the rain cover body, so as to prevent the insulating rodfrom being wetted by the rain. The common adjustable rain cover is suitable for insulating rods with different diameter sizes, and is good in commonality and flexible and convenient to mount and dismount.