The invention discloses a work bucket leveling system of a high-altitude operation car. A main valve can be a cartridge valve or a multi-way valve. Maximum load pressure of a telescopic oil cylinder and maximum load pressure of an amplitude-variable oil cylinder are both fed back to a load-sensitive oil port LS of a constant pressure drop variable pump. A reversing valve is arranged on an oil waywhere a pressure oil port P of the main valve and a pressure oil port P of a leveling valve are connected, when the reversing valve is located at a spring position, the pressure of the pressure oil port P of the leveling valve is zero, during reversing of the reversing valve, a pressure oil port P of the constant pressure drop variable pump communicates with the port P of the leveling valve through a speed-regulating valve, pressure of the port P of the leveling valve is fed back to the load-sensitive oil port LS of the constant pressure drop variable pump through a one-way valve connected tothe position of an oil outlet of the reversing valve. Leveling of a work bucket is convenient to control, the leveling action is free of lag, system response is rapid, meanwhile, the system is alwaysa load-sensitive system, and energy saving and consumption reduction are achieved.