The effect of different nitrogen fertilizers on dynamic transformation of phosphorus fertilizer in calcareous soil was studied in indoor incubation experiments. The results showed that except ammonium nitrate, all nitrogen fertilizers decreased soil available phosphorus content, especially calcium nitrate and urea; and that all nitrogen fertilizers de- creased soil water soluble phosphorus content, but the effect of ammonium nitrate was less than that of the others; and that difference in soil water soluble phosphorus among these different nitrogen fertilizers was biggest great on the fifteenth incubation day, with calcium nitrate and urea was less than that of ammnonium chloride and ammonium sulphate. But with time going on except ammonium nitrate, the difference became little.