Automobile crane and multi-section telescopic arm device thereof

The utility model relates to an automobile crane and a multi-section telescopic arm device thereof. The multi-section telescopic arm device comprises a telescopic oil cylinder installed between a first section arm and a second section arm, a first extending arm rotating wheel fixed on the second section arm, a first extending arm draw cord bypassing the first extending arm rotating wheel and with two ends fixed on the first section arm and the second section arm respectively, a telescopic arm rotating wheel group arranged between a third section arm and a fourth section arm, a telescopic arm draw cord bypassing the telescopic arm rotating wheel group and with two ends fixed on the first section arm and the third section arm respectively, a withdrawing arm rotating wheel group arranged between the first section arm and the second section arm, and a first withdrawing arm draw cord bypassing the withdrawing arm rotating wheel group and with two ends fixed on the second section arm and the fourth section arm respectively. The automobile crane with the multi-section telescopic arm device is further provided. The multi-section telescopic arm device achieves synchronous telescoping of a multi-section telescopic arm through the single telescopic oil cylinder, reduces weight of more than one ton for a hoisting arm, and namely reduces the weight of the whole crane. In addition, self weight of the hoisting arm is reduced so that stability of the whole crane in operation is improved.