Although thermoplastic composites have many attractive physical properties including toughness and high strength, they have not been used widely due to poor processability. In this study, the unidirectional composites were fabricated under different molding pressures and holding time using parallel yarn which consists of 30, 40 and 50 volume percent of glass fiber. The mechanical properties of PET/GF composite were investigated by ILSS and DCB (double cantilever beam) methods. The relationship between molding conditions and mechanical properties were discussed. Moreover, observation of fracture surfaces using SEM clarified the influence of molding conditions on fracture behavior. As a result, it was also observed that severe increase in molding pressure caused extrusion of resin and increase in void fraction, which in turn to decrease in fracture toughness.