Crane single-cylinder bolt telescopic system and crane

The invention discloses a crane single-cylinder bolt telescopic system and a crane. The system comprises a hydraulic oil tank, a reversing mechanism, a first hydraulic cylinder, an adjusting mechanism and a second hydraulic cylinder which are connected in sequence, the reversing mechanism is used for switching a connecting oil way between the hydraulic oil tank and the first hydraulic cylinder; the second hydraulic cylinder comprises an arm pin oil cylinder and a cylinder pin oil cylinder. The adjusting mechanism is used for controlling the communication relation between the first hydraulic cylinder and the arm pin oil cylinder and between the first hydraulic cylinder and the cylinder pin oil cylinder. A balance valve and a control mechanism are further arranged between the reversing mechanism and the first hydraulic cylinder, and an oil inlet and an oil outlet of the balance valve are connected between the reversing mechanism and a rodless cavity of the first hydraulic cylinder in series. A control oil port