The effects of rainfall intensity(RI) and rain-fertilization interval(RFI) on N export by runoff in oilseed rape land were studied with simulated rainfall and in situ soil pot experiment.The tested soil was collected from the surface layer(0~20 cm) of cole field,in Jiaxing city,Zhejiang province in Southeast China.Our results show that: firstly,N concentrations in runoff increase with the increase of RI and decrease with the increase of RFI.The process of N export by runoff can be separated into two steps,i.e.,fluctuation step and stable step,and there is a high loss risk for N in the fluctuation step.Nitrate-N is the predominant N form in runoff,with the ratio of nitrate-N/TN more than 0.3 in all treatment.This study indicates that high RI and short RFI would enhance N loss by runoff greatly,and suggested that fertilization should be taken at RFI>5~7 days,so that N loss by runoff could be largely mitigated.