A field plot experiment with 4 phosphorus application rates in 4 replications was conducted on the calcareous paddy soil in the Jianghan Plain under rice plant in the year 2005,in order to estimate the loss risk of phosphorus.Results show that: the P concentration in surface water has great relation with the P application rate,so considering of the environment impact,economic benefit and the need amount P of rice growth,we recommend the P application rate is 66 kgP2O5/hm2 by linear plateau model;during the days after P application,the concentration of P in surface water takes on a course that fall rapidly at first,then fall slowly and to be steady,and the P concentration of the surface water still keep high in 7 days after P application,so it is dangerous for P drainage;the logarithm model related to time can predict the concentration trend of the P(except SOP),r is 0.715 1 ~0.963 9(P<0.05),so we can utilize this model to predict the drainage safe time,and we find the safe time for water drainage is about 24 days after P application under the common P application rate;the soluble inorganic phosphorus(SIP) is main form of the total phosphorus(TP) in surface water,except the treatment P0,and the particulate phosphorus(PP) increases along with the increase of P rate,it indicates that the influence of PP can not be neglect when we estimate the P surface water contribute to the water eutrophication.