Soybean seeds of Fengdou-101 were implanted by N,+, ions. Cotyledon samples (24h, 96h) were collected randomly during cotyledons to primary leaves seedlings stage for testing. The effects of N,+, ion (E=25kev) implantation (0—10.4×10,16,N,+,/cm,2,) on the activities of peroxidase(POD), catalase(CAT) and superoxides dismutase(SOD), content of malondiadehyde(MDA) and leakage of electrolyte were investigated in soybean seedlings. The results show that the SOD and CAT were the highest with doses from 6.5×10,16, to 7.8×10,16,N,+,/cm,2,. The POD activity kept relatively stable level when the dose was lower than 5.2×10,16,N,+,/cm,2, whereas the POD activity increased gradually with increasing doses above the threshold of 5.2×10,16,N,+,/cm,2,. The N,+, ion implantation of soybean seeds reduced the accumulation of MDA and electrolytic leakage of cotyledons, and the lowest MDA content and the electrolyte leakage was found at 6.5×10,16,N,+,/cm,2,. It indicates that N,+, ion implantation may reduce lipid peroxidation and improve the ability of cold acclimation in soybean seedlings.