Abstract--- Reinforced thermoplastic composites used for primary aircraft structures are subjected to thermal effects throughout their lives. That is why the understanding of the temperature impact on the mechanical properties of glass fiber reinforced plastics is very important for the choice of the appropriate plastic for aircraft design. Polyphenylene sulphide (PPS) has been commonly used in high-performance composites as a matrix component. In this research, PPS and 40% glass fibers reinforced PPS composites are used. The impact transition behavior of PPS and its composite were studied by evaluating the impact test at temperature range (TRoom ? 23?C, -26?C and -78.5?C). The low temperatures (-26?C and -78.5?C) were obtained by using a specific Refrigerator and a dry ice, respectively. In addition, the morphologies of PPS and its composite surfaces fractured by charpy impact test were investigated by scanning electron microscopy (SEM). DSC Test is used to study the crystallinity of PPS and 40GF PPS composite. And the results show that the crystallization of pure PPS is higher than 40GF PPS. The results indicate a mechanical properties dependency of PPS and PPS composite reinforced with glass fibers on temperature. PPS shows a ductile behavior at room temperature and the behavior turns to be brittle as the temperature decreased to reach -26?C. While 40GF PPS composite show a brittle behavior at room temperature and turns to be ductile as temperature decreased to reach -26?C.