Office chair back structure capable of being adjusted to ascend and descend

An office chair back structure capable of being adjusted to ascend and descend comprises a chair back frame, a chair back body, a fixing seat and a lifting seat, and the chair back body is arranged on the lifting seat; a lifting groove is formed in the back of the lifting seat, the fixed seat is arranged in the lifting groove, and the other end of the fixed seat extends out of the lifting groove and is connected with the chair back frame; a lifting groove is formed in the chair back frame, a height locking cavity is formed in the lifting groove, a plurality of height locking grooves are formed in the height locking cavity, a fixing groove is formed in the end, back on to the chair back frame, of the fixing seat, and a height locking mechanism matched with the height locking grooves to lock the height position of the lifting seat is arranged in the fixing groove. The height locking groove, the height locking mechanism and other structures are not exposed out of the office chair, so that the defects in the prio