The continuous glass fiber-reinforced polyarylene ether nitriles (PEN) composites were successfully fabricated from PEN pre-impregnated glass fabric mates and PEN films using a film-stacking method. The work involved heat treatment for crosslinking reaction of PEN, and so it provided an interesting comparison of how heat treatment can influence the properties of composites. Detailed study on heat treatments for crosslinking reaction of PEN in the catalysis of the ZnCl2 at high temperature promoting the thermal and mechanical properties of composites were also investigated. The results showed that the thermal and mechanical properties of composites were enhanced by heat treatment, which is due to the fact that PEN resins could be crosslinked by the catalytic action of ZnCl2 at high temperature and formed triazine rings with a more thermally stable structure.