A jib crane in a shield tunneling machine inverted-arch block conveying system comprises a support. An upper hinged base and a lower hinged base are arranged on the side of the support. The upper hinged base is connected with a turning base. The upper end of the turning base is hinged to the upper hinged base. The lower end of the turning base is provided with an electric pushing rod. The outer shell of the electric pushing rod is hinged to the turning base. The end of a rod of the electric pushing rod is hinged to the lower hinged base. A jib is arranged on the turning base. A sliding trolley is hung on the jib. A sliding wheel of the sliding trolley is matched with the jib. An electric hoist is fixedly arranged on the bottom of the sliding trolley. The jib crane is directly inserted into a tunnel, inverted-arch blocks are lifted through the electric hoist, the inverted-arch blocks are conveyed through the sliding trolley along the jib, operation is easy, space is small, using is flexible, the jib crane can be used in a small tunnel environment conveniently, in a tunnel with a gradient, by stretching of the electric pushing rod, the jig is kept horizontal, so that the fact that the sliding trolley moves horizontally is kept, balanced stress of parts is kept, the problem that the sliding trolley slides along an oblique track is avoided, and accordingly the safety of a using process is improved.