Na_xTi_nO_2n+1 whisker was prepared by Na⁺/H⁺ ion-exchange on layered hydrous titanium dioxide, H₂Ti₄O₉·nH₂O. The ion-exchange reaction proceeded at various mole concentration of NaOH solution that the host framework of [Ti₄O₉^2-]_n was remained unchanged. And the ion-exchange phase identified the phase transition through the heat treatment at various temperature. As the result of this experiment, NaHTi₄O₉·nH₂O was decomposed into Na₂Ti₆)O₁₃ and TiO₂ in the temperature of 200℃∼600℃.