The characteristics of nitrogen and phosphorus loss from rice field by natural rainfall runoff were studied in Shuangqiao Farm of Jiaxing city, located at the Yangtz river delta region. The experiment was conducted using the fifteen plots method with an irrigation water-supported system. From results, we could get these information as follows: firstly, the highest total nitrogen (TN) concentration was 22.15 mg/L, and 4.84 mg/L for total phosphorus (TP) which exceeded more than the criterion for TN and TP regulated by our national government. Secondly, dissolved nitrogen was the predominant losing nitrogen form in runoff, of which nitrate nitrogen had about a percentage of 40~80, and 3.4~27 percent only for ammonium nitrogen, however, there was 76~79 percent of particular phosphorus moving in runoff. Thirdly, the discharge of nitrogen and phosphorus with runoff losing from rice field was 0.23~0.80 kg/hm~2 and 0.07~0.15 kg/hm~2 respectively, which both was less than one percent of the nitrogen fertilizer input. Finally, it was found that rainfall and fertilizer were two main factors influencing nitrogen and phosphorus loss in runoff, and there was a significant relativity among rainfall, fertilizer input and nitrogen and phosphorus loss load.