disclosed is an apparatus for preparing phosphoric acid from a fume exiting the kiln in a kiln phosphoric acid process , the apparatus comprises a hydration tower and an acid solution cyclical spraying system , a fume inlet of the fume exiting the kiln is disposed at a lower portion of the hydration tower , a fume outlet after hydration and absorption is disposed at the top , a spraying device is disposed in a cavity of the hydration tower above the fume inlet , a liquid inlet of the acid solution cyclical spraying system is disposed on a bottom of the hydration tower , a liquid outlet of the acid solution cyclical spraying system is connected to a liquid intake pipe of the spraying device . the present invention has the advantages of simple structure , reasonable layout , strong adaptability , high raw material utilization rate , reduced contaminant emissions , and high recovery rate of phosphoric acid etc .