The invention discloses a hydraulic system of a wide-body dump truck. The hydraulic system is characterized by consisting of a hydraulic oil tank, an engine, a power steering pump, a high pressure filter, a reversing valve, an energy accumulator, a cooling pipeline, a steering gear, a steering actuation cylinder, a gearbox PTO, a lifting pump, an oil return filter, a lifting cylinder, an air control reversing valve and a connecting pipeline; the power steering pump is connected with the engine, and the lifting pump is connected to the gearbox PTO through a transmission shaft; the power steering pump is connected to the reversing valve after passing through the high pressure filter; two oil passages are formed after passing through the reversing valve, one oil passage is connected to the energy accumulator and the steering gear to supply oil to a steering system, and the other oil passage is connected with the air control reversing valve after passing through the cooling pipeline and supplies oil to a hydraulic lifting system; and emergency steering is realized, the safety is improved, the oil temperature of the hydraulic system is significantly reduced, and the cleanliness of the hydraulic oil is improved.