Telescopic system capable of preventing core tube from inhaling empty and crane

The invention relates to a telescopic system capable of preventing a core tube from inhaling empty and a crane, wherein the telescopic system capable of preventing the core tube from inhaling empty comprises a telescopic cylinder, a telescopic control valve, a switch valve, a cylinder pin cylinder, an arm pin cylinder and a hydraulic circuit connected among the telescopic cylinder, the telescopic control valve, the switch valve, the cylinder pin cylinder and the arm pin cylinder; the telescopic cylinder is used for driving the cylinder pin cylinder and the arm pin cylinder to find an arm position, and is internally provided with the core tube; the telescopic control valve is used for controlling the passing and breaking of an oil supply line for supplying oil into the core tube; the switch valve is used for controlling the core tube to supply oil into the cylinder pin cylinder, or supply oil to the arm pin cylinder; the core tube is also connected with an oil supplementing line, and when the telescopic control valve disconnects the oil supply line and the core tube inhales empty, oil is supplemented into the core tube through the oil supplementing line. According to the telescopic system and the crane, the core tube can be prevented from being damaged due to inhaling empty and the reliability of the telescopic system is improved.