The safety and sustainability of greenhouse vegetable production are seriously threatened by the frequent occurrence of root knot nematode disease. To explore the effects of nitrogen (N) fertilizer application rate and soil sterilization on root knot nematode infecting tomato roots, a pot experiment was carried out with a twofactorial (N application rate and soil sterilization) randomized block design. The N application rates were 100 and 300 mg·kg^-1. Soil sterilization included gamma ray sterilization and nosterilization. The results showed that the root knot numbers per unit root length and unit root dry weight in low N application rate were reduced by 42.5% and 30.4%, respectively, as compared to high N application rate under the non-sterilization condition, while the dry weight of shoot and root increased by 43.9% and 31.4%, respectively, and agronomy use efficiency of N increased by 4.3 times. Gamma ray sterilization effectively eliminated the infection of root knot nematodes to tomato roots and the aboveground dry weight increased by 31.8%. Appropriate reduction of N application rate can significantly reduce root knot nematode infecting to tomato roots, promote tomato growth, and improve N agronomy use efficiency.