The changes of cellulose microstructure after implanted by low energy N,+, were characterized by IR, X-rays diffraction and SEM. The results showed that the cellulose intra-molecular and the intermolecular hydrogen bond have broken after implanted by low energy N,+,. With the increment of implanted ion doses, the cellulose relative degree of crystallinity reduced gradually. When the implantation doses increased to 1500×10,14, cm,-2, the relative degree of crystallinity decreased 6.84% compared with the control sample; and the cellulose particle diameter reduced gradually too, the fiber became more and more incomplete. There were obvious laminations on the surface of fiber, and mostly were tiny fragment.