Double roller extrusion granulator is particularly effective in granulating ammonium bicarbonate, ammonium chloride and monoammonium phosphate. The granulation rate can reach 85%. It adopts no drying process, room temperature granulation, one-time molding, low investment, quick effect, good economic benefit and small footprint. The roller granulator has wide adaptability to raw materials and can be used for granulation of various raw materials such as compound fertilizer, medicine, chemical, feed, coal, metallurgy, etc. It can produce various concentrations and types of compound fertilizer. The granules made are flat and round. There is no emission of waste water and waste gas.