An experiment was conducted in a wheat field of Heilu soil in the south of the Loess Plateau, Changwu County, Shaanxi Province. Efficiencies of urea use and water use were studied in a plot field experiment. Meanwhile the fate of applied nitrogen was investigat ed with ¹⁵N isotope technique. Results showed that crop response to N applied at the rate of 100kg hm^-2 was higher with productiv ity index of 12.1kg grain kg^-1 N, than at the rate of 150kg hm^-2 with productivity index of 6.4kg grain kg^-1 N. Nitrogen application increased water use efficiency from 7.6kg hm^-2 mm^-1 to 9.7~10.5kg hm^-2 mm^-1. ¹⁵N study showed that plant recoveries were in the range of 36.6%~38.4%; N remaining in 0~40 cm soil ranged in 29.2%~33.6% and decreased rapidly with increasing soil depth. About 33%~40% of the N taken up by wheat was derived from the urea applied and the rest, around 2/3 derived from the soil.