The invention discloses a method for producing anhydrous ammonia by absorbing ammonium phosphate, comprising the following steps: sending coke oven gas from the upper procedure to an ammonia absorption tower and being countercuttent contacted with ammonium phosphate poor liquid sprayed by the tower top; continuously extracting rich liquid from the tower bottom of the ammonia absorption tower and then carrying out the pre-treatment on the rich liquid; leading the pre-treated rich liquid after the temperature is increased by heat exchange to enter a degasser for flash evaporation and heat exchange and be sent to the upper part of a desorption tower after that; heating by a heater at the tower bottom of the desorption tower with the adoption of heat conduction oil; sending ammonia gas which is escaped from the tower top of the desorption tower to a rectification tower after condensation and cooling, heating by the heater at the tower bottom with the adoption of the heat conduction oil, stripping and rectifying ammonia water, thereby obtaining a colorless high-purity liquid anhydrous ammonia product which is not less than 99.8 percent by weight. The use of the invention can reduce thepower consumption during the ammonia absorption process by 60 percent, reduce the operation cost, be applicable to the construction in cold areas, reduce the amount of discharged sewage by 60 percent-80 percent compared with the traditional process, eliminate the pollution of waste gas to the environment, have low manufacturing difficulty of equipment and be convenient to install and troubleshoot.