Abstract: Current study shows that range distribution of ions implantated into plant seeds obtained with TRIM program are far from experimental data. According to characters of microstructure of plant seeds, microstructure models and calculation programs are designed. With Monte-Carlo simulation range distributions are calculated for iron ions implanted into peanut, color cotton and wheat seed at different energies (110 keV, 20 keV, 200 keV) and different doses (2×10¹⁶ ions·cm^-2, 5×10¹⁶ ions·cm^-2, 10¹⁷ ions·cm^-2, 2×10¹⁷ ions·cm^-2). The results agree well with experimental results. A random sampling simulation method is obtained for interaction between implantation ions and seed microstructure, which provides an idea for theoretical study of interaction between implantation ions and organisms.