Abstract: Based on long-term measurement of N and P concentrations in the agricultural headwater ditches during the planting period of rice, the characteristicsof N and P export, transportation and transformation in the headwater ditches adjacent to rice field were studied. The results showed that in the experiment time the highest TN export mass concentration was 4.00 mg/L, and ammonium and nitrate were the predominant forms with the highest export mass concentration being 3.00 and 1.83 mg/L, respectively. The soluble phosphate was the predominant form of phosphorus and TP and phosphate mass concentration reached 1.00 mg/L. The export concentration of N and P from the ditches declined with time after irrigation. During raintime, duo to the change of loss pattern, the export concentration of N gradually increased for 2～3 d before declined, and the loss of phosphate was at the lowlevel. The N and P concentration at different sections showed similar trend, which explained that the retentions on N and P in the ditches system were stable. In this situation, the TP mass concentration declined with time, while TN and NH₃-N concentrations gradually declined with time after irrigation, increased somewhat after rainfall, but had the trend of decline finally.