Single crab of crane

The present invention relates to a single crab of crane. It is characterized by changing the upper pulley device of auxiliary lifting mechanism of general crane into upper pulley crab structure, i. e. a trackway identical to the crab running direction is laid on the crane crab frame, and the upper pulley crab can be run along this trackway. The motion of said crab is implemented by means of running supporting mechanism formed from motor, actuating element and connecting component, so that the distance between hanging point of main hook and hanging point of auxiliary hook can be changed, and when it is necessary for crane auxiliary hook to cooperate with main hook t do work, said invention can implement automatic hanging and unhanging operation of auxiliary hook.