The bark and wood of the apple branches were separated and then made them into carbonized bark and wood in low oxygen at 450℃.The ultrastructural and adsorption to NH₄⁺-N and NO₃^--N of them were investigated. The results showed that the cellulose content in carbonized bark was higher than that in carbonized wood, and there were more microscopic holes and gullies in the carbonized bark, and the longitudinal gullies and pores were more developed after carbonization. The saturated adsorption capacity of the carbonized bark to NH₄⁺-N and NO₃^--N was 24.11 mg/g and 12.93 mg/g, respectively; while the corresponding parameter of the carbonized wood was 22.24 mg/g and 11.99 mg/g, respectively, and carbonized bark had stronger adsorption capacity to NH₄⁺-N and NO₃^--N than that of carbonized wood. The adsorption capacities of these two kinds of materials to NH₄⁺-N were greater than those to NO₃^--N. Freundlich and Langmuir isothermal adsorption models, pseudo second-order kinetic model and Elovich model could be used to fit the adsorption processes. Carbonized bark had stronger adsorption capacity, which was related to its higher cellulose content and more developed microscopic gullies.