The processing of cross-linked polyarylene ether nitrile (PEN), which has a triazine rings structure, has been investigated under different reaction times and temperatures. In this study, the PEN films prepared by the tape-casting formed the thermally stable triazine rings by catalytic cross-linking reaction gradually, which was characterized by Fourier transform infrared spectroscopy. The chemical cross-linking reaction occurred as the CN group absorption of PEN at 2221 cm Γ1 decreased and a new absorption peak, at 1682 cm Γ1 , was observed, and the absorption peak intensity would be progressively larger, with the extension of the processing time. After the formation of cross-linking networks, the cross-linking degree and thermal and mechanical properties of the processed films were improved substantially, compared with the untreated films. The film with added ZnCl 2 as the catalyst was more rapidly cross-linked, and its properties were better than that without catalyst at the same treatment conditions. The glass-transition temperature (T g ) of PEN films processed at 350 C for 4 h (213.65 C) was higher than that of PEN films before the treatment (161 C), and the tensile strength was also improved significantly. The PEN was processed at 350 C for 2 h, whose initial decomposition temperature increases by about 10 C, compared with that of untreated film, at one time. The rheology behavior of the cross-linked films was processed on dynamic rheometer to monitor and track the process of polymer cross-linking reaction. V