Polynaphthoxazines-clay nanocomposites were prepared from 1, 5-dihydroxynaphthalene, aniline, formaldehyde and different proportion montmorillonite(MMT) by in-situ reaction in ethanol. Dynamic TGA showed that nanocomposites have delayed decomposition temperatures when compared with pristine polynaphthoxazine indicating the enhancement in the thermal stability. Polynaphthoxazines-clay nanocomposites were prepared from 1, 5-dihydroxynaphthalene, aniline, formaldehyde and different proportion montmorillonite (MMT) by in-situ reaction in ethanol. Dynamic TGA showed that nanocomposites have delayed suspension temperatures when compared with pristine polynaphthoxazine indicating the enhancement in the thermal stability.