The effects of medium energy N ion beam irradiation on the germination and the growth of different kinds of wheat seeds are discussed in this paper. According to the results of test in laboratory and the field, the germination and the seedling growth of wheat seeds with irradiation dose were evidently inhibited. Furthermore, there was a larger difference between implantation and penetration. In the course of the seed germination the inhibition resulting from the implantation was clearly stronger than that from the penetration. From survival curves of emergence rates of three different strains in the field, the half-lethal doses of implantation and penetration (D,50,) are in the range of (10,7,~10,8,) ions/cm,2, and (10,8,~10,9,)ions/cm,2, respectively.