In order to study the differences of nitrogen loss between organic fertilizers and chemical fertilizerafter application in purplish soil,according to local agricultural habits in Chongqing,chemical fertilizer,swine manure (SM),oil cake (OC),biogas slurry (BS) and organic-inorganic compound fertilizer(OF) were selected to compare the characteristics of nitrogen loss by indoor simulating runoff experiment in purplish soil.The results showed that,under the experimental condition,total nitrogen contents in runoff fluid of fertilizer treatments were all significantly(P<0.01) higher than blank,with 3.4—9.1 times,while the differences between organic fertilizers and chemical fertilizer were insignificant(P>0.05).The order of total nitrogen loss rates of organic fertilizers relative to chemical fertilizer was SM>OF>BS>OC.The rainfall intensity,fertilizing amount and slope had significantly positive relation with runoff total nitro gen(TN) content in purplish soil (P<0.05),and slope was the most important factor for causing nitrogenloss,followed by fertilizing amount and rainfall intensity.Under the indoor simulating condition,particulate nitrogen was the main form in runoff, accounting for 52.51%—81.50% of TN, ammonium nitrogen(NH₄⁺-N) was higher than nitrate nitrogen (NO₃^--N),NH₄⁺-N occupied 11.44%—43.57% of TN and NO₃^--N only occupied 1.74%—14.55%. It presented that organic fertilizer application would cause nitrogen loss by runoff water in purplish soil,and nitrogen loss of organic fertilizer might be significantly higher than that of chemical fertilizer in a certain condition.Thus,different kinds of organic fertilizers should be applied reasonably in agricultural production,and fertilizing amount should be controlled.