N,+, ion implantation with different doses was used to screen sulfaguanidine resistance enhanced strains using ,Bacillus subtilis, HSD06 as an initial strain for mutation. It has been confirmed that the best implantion dose is 3×10,15, cm,-2, for resistance enhanced mutants. Two strains B11 and B13 with higher yield of inosine have been obtained from 528 mutants. Shake flask test shows that the yield of inosine reaches 14.83 g/L and 14.38 g/L with B11 and B13 respectively, which has increment by 16.3% and 12.8% respectively compared with that of initial strain.