The melting process of NC was examed by using MDSC technique,microscope carrier method and incorporation with the solid reaction cell/RSFT-IR. The experimental results show that the endothermic process in the MDSC curve is invertible. It is caused by the phase change from solid to liquid of the mixture of initial NC and partly decomposed products in condensed phase. The values of the melting point,melting enthalpy ( ΔH_m),melting entropy (ΔS_m),and the enthalpy of decomposition (ΔH_dec) and the heat-temperature quotient (ΔS_dec) obtained by the MDSC curve of NC at heating rate of 10K·min^-1 are 476.84K,205.6J·g^-1,0.4312J·g^-1·K^-1,-2475.0J·g^-1,-5.242J·g^-1·K^-1,respectively. The MDSC analysis results of NC with different nitrogen contents show that with increase of nitrogen content in NC,the absolute values of ΔH_m,ΔS_m,ΔH_dec and ΔS_dec increase.