In order to investigate the variation characteristics of soil nitrogen concentration in sandy loam greenhouse cucumber under different irrigation levels,with the weighing lysimeter test platform,3 treatments was set up according to the evaporation amount of the evaporator pan in diameter 20 cm in the greenhouse:I1(Kcp1:0.8),I2(Kcp2:1.0)and I3(Kcp3:1.2).The dynamic changes of nitrogen concentration and nitrogen leaching in different soils of cucumber were studied.The results showed that reducing the amount of irrigation,the concentration of nitrate nitrogen in the 20 and 40 cm increased,while in the 60 cm soil layer it decreased.Compared with treatment I3,the average concentration of nitrate nitrogen in the 20 cm and 40 cm increased by 75.59% and 134.36%,respectively,but decreased by 18.88% in 60 cm soil layer.Under different irrigation treatments,the maximum concentration of ammonium nitrogen in each soil layer was only 0.4 mg·L-1.The change of ammonium nitrogen in 20 cm soil layer was similar to that of nitrate nitrogen,while in 40 and 60 cm soil layers the difference were not significant.The total amount of nitrogen leaching in the 90 cm was 56.08~203.13 kg·hm-2,accounting for 9.02%~32.69% of total nitrogen application.Compared with treatment I3,I2 not only had the highest yield of cucumber,but also decreased the total amount of nitrogen leaching by 49.16%,and the irrigation water use efficiency and nitrogen fertilizer productivity increased by 39.24% and 18.88%,respectively.Considering the nitrogen concentration in the soil,leaching amount and cucumber yield,I2 treatment(Kcp2:1.0)was the best irrigation under the test conditions.