As a high-performance semi-crystalline thermoplastic composite material, the mechanical properties of carbon fiber reinforced polyether ether ketone (CF/PEEK) are closely related to its thermoforming process parameters. The material undergoes complex thermodynamic processes during the thermoforming process, so it is crucial to study its crystallization process with an accurate and practical crystallization kinetic model. Existing theoretical models for non-isothermal crystallization of thermoplastic composites are often difficult to obtain the parameters and have the problem that the final relative crystallinity cannot reach 1. For this reason, this paper proposes an improved nonisothermal crystallization kinetic model for thermoplastic composites based on the Mampel model using a new segmented functional form to simplify the expression of the crystallization rate function K(T), and analytically validates the model on CF/PEEK thermoplastic composites. The results show that the model can not only solve the problems of difficult to obtain the parameters of the existing models and the final relative crystallinity cannot reach 1, but also significantly improve the prediction accuracy of the relative crystallinity and crystallization rate of the non-isothermal crystallization process of CF/PEEK, thus verifying the reliability of the model.