In the previous work, we introduced new polymer blends from the advanced COPNA-resin and nylon 6.(1) The morphology of the polymer blends were quite different between the B-staged state and the fully cured state. In order to investigate a phenomenon occurred in the curing process, C-13 Fourier transform-nuclear magnetic resonance (FT-NMR) spectral analysis, N-15 FT-NMR spectral analysis, and Fourier transform infrared absorptional spectral analysis were carried out on the blends in a solid state. From the spectral analyses, it was revealed that a graft reaction occurred at the interface between the advanced COPNA-resin and the nylon 6. The difference of the morphology on the fully cured polymer blends was due to the following reason. In the curing process, generated benzyl-type cations of the B-staged Advanced COPNA-Resin initially attacked and combined with nitrogen in the amino groups of the nylon 6. In the late stage of the curing process, the cations mainly attacked and combined with pi electrons of the condensed aromatics.