Inorganic nitrogen leaching loss was estimated with porous pottery tube on a rice field at the Shenyang Ecological Experimental Station,Chinese Academy of Sciences.The results obtained could be summarized as follows: The ammonium leaching loss was negligible(< 2 mg/L)after N fertilization,but the leached amount of nitrate was increased with increasing N application rate,being 0.096~21.65 mg/L at 60 cm depth,and 0.87~14.91 mg/L at 90 cm depth.Water penetration rate had a strong effect on nitrate leaching.When the penetration was faster or nitrogen rate was higher,more than 10 mg/L of nitrate(the international sanitation standard of drinking water) was found in the leachate.The peak of ammonium and nitrate leaching loss was appeared soon after basal dressing,but at 10 days or more after tillering or earing stage-topdressing,and the loss amount was also higher after basal dressing.