The effect of different nitrogen fertilizers on dynamic transformation of phosphorus fertilizer in paddy soil under flooding condition was studied in indoor incubation experiments.The results showed that all nitrogen fertilizers hardly influenced soil available phosphorus on the first day incubation,while greatly reduced soil solution phosphorus.And then,the NH-4NO-3 and Ca(NO-3)-2 treatments increased both soil available and solution phosphorus notably,and the(NH-4Cl) and(NH-4)-2SO-4 treatments decreased soil solution phosphorus a little,affected soil available phosphorus little.And to the urea treatment,both soil available and solution phosphorus were increased on the fifteenth and thirty-fifth day incubation,and had little difference from the control on the seventieth and one hundred and fifth day incubation.