An in-situ field experiment was carried on to study nitrogen leaching from farmlands typical of the Three-Gorges Reservoir Region of Chongqing for three successive years (from 2005 to 2007)，using modified apparatuses packed with ion exchange resin and buried into the soil at the depth of 20 cm，30 cm and 40 cm，separately to adsorb NO₃^--N and NH₄⁺-N and hence to monitor nitrogen leaching from the two soils monthly and after each moderate and heavy rainfall event. It was found that nitrogen leaching from vegetable field (74.58 kg hm^-2 a^-1) was higher but that from on slope farmland (46.01 kg hm^-2 a^-1) was lower than nitrogen input (56.9 kg hm^-2 a^-1) with rainfall into the fields，which indicates that nitrogen leaching from vegetable fields may partially affect the local water environment，but the farmland as a whole may not be the major cause of eutrophication of the local water system.Of the total nitrate leached from the soil more than 90% was NO₃^--N and its leaching occurred mainly during the first moderate or heavy rainfall event after fertilization.And NO₃^--N leaching from soil layers followed the sequence of cultivated layer > subsoil layer > bottom layer，and the former was much higher than the latter two.Moreover，it concentrated mainly in the early part of the rainy season，peaking in May，and stayed low in the later part，rendering limited impact on waterbody.A positive exponent correlation was observed between nitrate leaching and soil alkalyzed N. Therefore，it seems that vegetable fields are the major object for control of soil N leaching and effective measures may include control of nitrogen fertilization rate，reduction of soil available nitrogen pool and suppression of nitrification in the soil.