Connecting joint, auxiliary arm mechanism and crane

The invention provides a connecting joint, an auxiliary arm mechanism and a crane, relates to the technical field of crane equipment, and aims to optimize the structure of the connecting joint to a certain extent and reduce the disassembly and assembly frequency among structures in the auxiliary arm mechanism. The connecting joint is used for connecting a main arm and an auxiliary arm mechanism and comprises a frame body, and the frame body comprises a first supporting rod, a second supporting rod and a third supporting rod; the two ends of the second supporting rod are connected with one endof the first supporting rod and one end of the third supporting rod correspondingly, and a first connecting part is formed at the joint of the second supporting rod and the third supporting rod and used for connecting a lower knuckle arm of the auxiliary arm mechanism; a second connecting part is arranged on the first supporting rod and used for being connected with a first mast of the auxiliary arm mechanism; a third con