Crane and method for unfolding fly jib thereof

The invention provides a crane which comprises a supporting base, a main arm and an auxiliary arm, the tail of the main arm is connected to the supporting base, the head of the main arm is connected with a pulley shaft, the pulley shaft is perpendicular to the length direction of the main arm, the auxiliary arm comprises a storage position and a working position, and when the auxiliary arm is located at the storage position, the auxiliary arm is located on the side of the main arm; the auxiliary arm is not connected with the main arm, when the auxiliary arm is converted into the working position from the storage position, the tail of the auxiliary arm is detachably connected with the pulley shaft through a connecting piece, the auxiliary arm rotates around the connecting piece, and the tail of the auxiliary arm is fixedly connected with the head of the main arm. According to the crane, the problems in the prior art can be solved, the mounting structure of the main arm and the auxiliary arm is optimized, and t