A field experiment was conducted on Chinese cabbage in Nanjing suburbs to investigate soil nitrogen supply, nutrient uptake by the vegetable and chemical N losses during its growing period. Results showed that the amount of N supplied to the crop by the soil in the 0~20 cm layer was 50.7 kg/hm², accounting for 1.07% of the total soil N in the layer. Application of N fertilizer significantly increased yield of Chinese cabbage by 3~4 times. More than 70% of the N taken up by Chinese cabbage was derived from chemical N fertilizer. In the field experiment, the apparent recovery rate of urea was 26%~35%. Nitrate content in the 0~40 cm soil profile increased with N application rate.