Abstract: A field plot experiment was conducted on two types of paddy soils,the permeable paddy soil in the Anzhen site and the waterlogged paddy soil in the Changshu site,in the Taihu Lake Region from June 2000 to June 2002 to explore phosphorus(P) loss by runoff and by drainage flow and its relation to Olsen-P concentration in the topsoil.The results showed that,under the conventional P application rate of P_(30)/P_(20),total P(TP) loss rate by runoff and by drainage flow was 603.2?g/(hm~2·a) during the 2000～2001,lower than that during the year 2001～2002 which was 1?148.9?g/(hm~2·a) in the permeable paddy soil.While in the waterlogged paddy soil at the Changshu site,it was 679.5 and 1?350.3?g/(hm~2·a) during the 2000～2001 and 2001～2002,respectively.Of the average annual TP losses from P_(30)/P_(20) plots in two years,63% was in wheat season and only 37% was in rice season in the peameable paddy soil,while in the waterlogged paddy soil more than 80% was in wheat season.Phosphorus application rate significantly affected TP losses by runoff or by drainage flow(p<0.01).The change-point of phosphorus losses by runoff is 32?mg/kg in the permeable paddy soil,greater than in the waterlogged paddy soil(26?mg/kg).This indicated that P loss by runoff in the waterlogged paddy soil would be probably easier than that in the permeable paddy soil.