Many historical archives have been deteriorated by aging with time. Various kinds of defects such as worm-hole, yellowing, brittleness are observed and their severity was dependent on raw material type, storage condition, and so on. For a long-term use and storage, a proper preservation treatment is required. Many studies on preservation and conservation have been carried out on hanji which was made from mulberry fiber, but there are few concerns on foreign paper. Therefore, aging and chemical strengthening treatment was done on paper made of bamboo and wood fibers depending on aging condition, the type and pickup weight of chemicals and treatment method. When methyl cellulose was treated with impregnation or brushing, the aged paper was strengthened effectively. The strengthening effect by chemicals was dependent on the aged condition of the paper.