The invention relates to a selective catalytic reduction urea air premixing jet system, which belongs to the technical field of diesel engines. The selective catalytic reduction urea air premixing jet system comprises a controller, a metering pump, a urea solution tank, a urea solution pressure-stabilizing cavity, a reflux valve, a jet electromagnetic valve, an air atomizing nozzle, an air electromagnetic valve, an air pressure-stabilizing cavity, an air pressure-reducing valve, a compressed air tank, a cooling liquid electromagnetic valve, an integrated heat exchange device, a pipeline heat exchange device and a urea solution tank heat exchange device. The selective catalytic reduction urea air premixing jet system has the characteristics of low energy consumption, high accuracy and stability, simple structure, low system development cost and manufacturing cost and capacity of effectively reducing fuel oil consumption and NOx emission of the diesel engines.