The invention relates to an emergency two-circuit power steering system, which comprises a main oil tank and an auxiliary oil tank, wherein the main oil tank is communicated with a steering engine and a steering assistance cylinder through a main steering pump to constitute a main steering system, the auxiliary oil tank is communicated with the steering engine and the steering assistance cylinder through an emergency pump and an emergency valve to constitute a steering emergency system, and the steering emergency system can ensure oil supply to the steering engine when the main steering system is failed and can not work normally so as to maintain the normal work of the steering engine. When an engine and the main steering system are failed, a running vehicle is enabled to have a steering capacity, the steering performance of a heavy vehicle, particularly the steering performance under an overload state, is improved, and at the same time the service life of the steering oil pump is prolonged. Through verification, when vehicles of the same type are provided with different steering systems, the service life is prolonged by more than 2 times.