Abstract: Poly(butylene terephthalate) (PBT), a semicrystalline polymer belonging to polyester family, is widely used in engineering applications due to its versatile combination of mechanical and thermal properties, chemical resistance, and high rates of crystallization. The physical and mechanical properties of the product are directly related to the microstructure, which is determined by the extent of crystallization and influenced by the nonisothermal conditions set forth during practical processing. Therefore, the nonisothermal crystallization kinetics can be used to clarify the crystallization behavior and provide a theoretical basis for the formation of crystals. In this paper, the epoxidized ethylene propylene diene rubber (eEPDM) was first successfully prepared by the epoxidation of ethylene propylene diene rubber (EPDM) using t-butyl hydroperoxide as an oxidant and molybdenum oxide as a catalyst. The prepared rubber was characterized by Fourier transform infrared spectroscopy (FT-IR) and ¹H-nuclear magnetic resonance (¹H-NMR). Then the PBT/Glass fiber (GF)/eEPDM composites with different eEPDM contents were prepared in a twin-screw extruder. The influence of eEPDM on the nonisothermal crystallization kinetics of PBT/GF was investigated using differential scanning calorimetry (DSC). The phase structure of PBT/GF/eEPDM was observed by scanning electron microscopy (SEM). Analysis of the crystallization data by Mozhishen model revealed that the presence of eEPDM could accelerate the nonisothermal crystallization rate of PBT in PBT/GF/eEPDM. The result was further proved by the effective activation energy calculated by Friedman method. The observation of SEM demonstrated that the interface performance was excellent among PBT, GF and eEPDM phases. Meanwhile, the mechanical properties of the specimens were evaluated.