This work presents a detailed study of deep and shallow level defects in nitrogen implanted n-type GaAs. Deep-level transient spectroscopy (DLTS) measurements show four electron traps and one hole trap in 140 keV nitrogen implanted GaAs after a dose of 1×1013cm-2 and a thermal annealing at 800℃ for 30 min: E1(0.111) ,E2(0.234) ,E3(0.415) ,E4(0.669) ,and H(0.545). Meanwhile,only E4 and H(0.545) defects are observed in 10 keV nitrogen-implanted GaAs after a dose of 5×1014cm-2 and the same annealing treatment. It oncluded that E2 and E3 correspond to the damages due to the high-energy implantation, E4 may be complex of intrinsic defect and implantation damage, H(0.545)is a nitrogen-related deep-level and may contribute to the free-carrier compensation in the nitrogen-implanted n-type GaAs.