The invention relates to a method for preparing granular and high concentration composite fertilizer of ammophos urate and potassium ammophos urate by employing revolving steel belt freezing pelletizer, , comprising: adding the measured urea, ammonium phosphate and potassium chloride or urea and ammonium phosphate into the fusion still equipped with coil pipe heated by steam for fast fusion to produce composite eutectic mixture based on urea; adding microelement addictive, then delivering the composite eutectic mixture with screw bolt equipped with insulating sleeve into the distributing device of the revolving steel belt freezing pelletizer, to make it drop homogenously in the steel belt rotating at uniform speed in the lower of the distributing device, freezing and solidifying for forming. The formed ammophos urate and potassium ammophos urate is measured packed with automatic packing machine for ex-factory. The invention is characterized by the short process, small investment, low energy consumption, no addition of material for freezing and solidifying and no drying, high granulation rate, uniform granule, good flowability, no lumping, no need for breaking with screen, cancellation of the treating course of material return, granulation, drying, cooling, breaking, bolting and exhaust gas treating which pollute environment in the traditional composite fertilizer producing course. |