In view of the situation of the low agricultural irrigation water utilization rate and the problem of environmental pollution caused by blind application of nitrogen fertilizer，a field experiment was conducted to study on the effects of soil water content and nitrate nitrogen transport under three kinds of drip irrigation with plastic film and furrow irrigation in Shiyang River basin of Gansu province.The research results showed that soil water content was mainly distributed in 0-60 cm layer，which was in good agreement with the root layer of tomato under drip irrigation with plastic film.It was beneficial to the absorption of soil water content by tomato roots.The nitrate nitrogen content changed little over time in drip irrigation and the nitrate nitrogen content changed large over time under furrow irrigation.The nitrate nitrogen content was higher in the depth range of 0-40 cm under drip irrigation with the soil water potential of -30 kPa and the nitrate nitrogen content was lower below 40 cm.The distribution of nitrate nitrogen content was not obvious under drip irrigation with the soil water potential of -50 kPa and -20 kPa.The way of absorption of nitrate nitrogen in the crop root layer and preventing the deep loss of nitrate nitrogen were best under drip irrigation with the soil water potential of -30 kPa.Therefore，the irrigation practice of drip irrigation under plastic film with soil water potential of -30kPa can help improve soil water and fertilizer use efficiency，and also can reduce the environmental pollution caused by nitrogen fertilizer.