The thermal transitions of a nylon 6/layered silicate nanocomposite were studied by differential scanning calorimetry and in-situ synchrotron X-ray diffraction. The drawn film of the nylon 6/layered silicate nanocomposite typically showed three endotherms in the DSC thermogram; a very broad endotherm at $sim120^{circ}C(T_{1})$, a double-melting endotherm at $sim215^{circ}C(T_{2})$, and a high temperature endotherm at $sim240^{circ}C(T_{3})$. The drawn film of the nylon 6/ layered silicate nanocomposite was comprised of a mixture of the $alpha and gamma$ forms, with $the alpha form$ being generated by drawing the pressed film having $the gamma form$. The melting and crystallization of the crystals were observed at the above thermal transitions during the heating experiment performed at the Pohang X-ray synchrotron radiation source (4C2). The newly generated form was meta-stable and melted $at {sim}T_{1}$. The double-melting $at {sim}T_{2}$ was due to the exothermic crystallization of $the alpha form$ during the main endothermic melting of $the gamma form$. $The alpha form$ crystallized $at {sim}T_{2}$ and melted $at {sim}T_{3}$.