The invention discloses a tower body erecting and descending mechanism for a tower crane. The tower body erecting and descending mechanism is installed on a tower body and a rotary table. The tower body comprises an upper tower body and a lower tower body which are hinged to each other, and the upper tower body comprises an inner tower body and an outer tower body which are sleeved with each other. The tower body erecting and descending mechanism comprises a connecting assembly, a tower pulling assembly, a tower pulling assembly, a jacking assembly and a locking assembly. The tower pulling assembly, the jacking assembly and the locking assembly are connected with the tower body respectively through the connecting assembly. The upper tower body and the lower tower body are driven to rotate through the tower pulling assembly, erection of the tower body is achieved, the inner tower body is jacked up through the jacking assembly and is safely and reliably locked at a target position through the locking assembly, tower body erecting and descending movement is flexible and rapid, the safety coefficient in the tower body erecting and descending process is greatly improved, and the tower body erecting and descending mechanism has the advantages of being simple in structure, simple and convenient to operate, wide in applied range, safe and reliable and the like. The invention further provides an erecting and descending method for the tower body erecting and descending mechanism.