In lysimeters,the transformation and accumulation of NO₃^--N in surface layer and its leaching loss out of 130cm solum column in chao soil in Beijing were studied by the routine analysis methods in combination with isotopic technique.The results showed that N transformation to NO₃^--N could be observed during the earlier growth stage.The significant differences existed among the treatments applied at 3 rates of urea but could not be found among the those with 3 kinds of N fertilizers. And the transformation to NO₃^--N was less strong during spring wheat growtk period than during summer corn growth period.Meanwhile immobilization and uncounted loss of fertilizer N could occur.NO₃^--N could be leached ont of 130cm soil body during rainy season with more than l Omg NO₃^--N/L in the fertilized lysimeters where the mean NO₃^--N content might be np to 33 mg/L.And NO₃^--N leaching loss was significantly correlated to the precipitation.However,the total leaching loss rate of fertilizer N was not high.