Glass fiber (GF) reinforced phenolphthalein-based polyarylene ether nitrile composites were prepared through melt blending, and the composites were characterized by various methods to find that both the mechanical and thermal properties of the silane coupling agent treated GF reinforced composites were improved with the increase of GF content. Tensile strength, flexural strength and Izod impact strength got their highest values with GF content at 35 wt.%, 30 wt.% and 25 wt.% respectively. The heat distortion temperature (HDT) of 30 wt.% GF reinforced composite is 284