Abstract: The influences of optimized fertilization on the nitrate nitrogen leaching, the yield of spring tomatoes and the economic benefit were studied using on site monitoring of ground water NO-3 method in the greenhouse located in Xushui, Hebei Province, where spring tomatoes had been planted for over 11 years. Four treatments with triplicates were designed: 1) Only phosphorus and potassium fertilizers (CK); 2) Manure plus phosphorus and potassium fertilizer (OM); 3) Manure plus conventional chemical fertilizer (MCC); 4) Manure plus optimum fertilizers (MOC). The results show that the yield is increased by 4.1%, the profit increased by 4.5% and the N use efficiency (%) improved by 1.48% with the optimized fertilization treatment (MOC) compared to the conventional way (MCC). The annual absoluteNO-3- N leaching amount decreased by 50.06 kg/ha under optimum fertilization treatment compared with the conventional fertilization treatment in 2011, when the annual precipitation at the fallow period was 465.3 mm. Therefore, decreasing the nitrogen fertilizer is the most effective way to reduce the leaching of nitrate nitrogen.