Abstract: Continuous glass fiber (GF) reinforced poly(cyclic butylene terephthalate) (PCBT) composites were prepared via in-situ polymerization of cyclic butylene terephthalate (CBT). The effects of the catalyst contents on the crystallinity and the mechanical properties of GF/PCBT composites were studied. When the catalyst mass fraction reaches 0.5%, the crystallinity is 53% and the GF/PCBT composites show the highest values of mechanical properties, tensile strength 522 MPa, tensile modulus 27 GPa, flexural strength 481 MPa, flexural modulus 24.8 GPa and interlaminar shear strength (ILSS) 43 MPa. The SEM results show good bonding quality between the fiber and the matrix at 0.5% of catalyst. The effects of quenching and annealing treatments on the mechanical properties of GF/PCBT composites were further investigated. The results show that the improved mechanical properties after annealing treatment, tensile strength is 545 MPa and flexural strength is 495 MPa.