In order to study the effect of nitrogen content on pyrolysis process of NC，Fourier Transform Infrared spectrometer (FTIR)，thermogravimetric analysis(TG)-FTIR and pyrolysis(Py) gas chromatography(GC)/mass spectrometry (MS) are used to reveal the structural characteristics，pyrolysis characteristics and process products of NCs with different nitrogen content. The results show that with the increase of nitrogen content，the amount of substituted nitro of NC increases，the pyrolysis reaction rate and reaction degree increase，the proportion of light gas increases and the product types increase，and a variety of chemical recombination forms appear at high temperature. In the pyrolysis process of NC，de-nitration reaction takes place first，and then large molecules are decomposed into small molecules，and then carbon skeleton and ring oxygen bridge fracture occurs. By identifying the common products of NC with different nitrogen content and the main nitrogen oxides in each stage，a mechanism of NC pyrolysis process based on the principle of temperature division is established.