Cantilever crane anti-tilting device, cantilever crane system and crane

The invention discloses an anti-back-tilting device for a cantilever crane, a cantilever crane system and a crane, relates to the field of crane hoisting, and is used for reliably preventing the cantilever crane from tilting backwards. The cantilever crane anti-back-tipping device comprises a sleeve, a core tube and a limiting assembly. The sleeve comprises a sliding hole and a positioning hole which are communicated with each other; and the positioning hole penetrates through the wall body of the sleeve. One end of the core tube is slidably inserted into the sliding hole of the reinforcing tube. The limiting assembly is rotatably mounted on the outer wall of the reinforcing pipe; in the process that the included angle of the sleeve is changed relative to the ground, the limiting assembly is constructed to be unchanged relative to the included angle of the ground, so that the positioning hole of the sleeve automatically rotates to the position clamped by the limiting assembly. According to the technical schem