Abstract: This study focuses on pultruded glass fiber reinforced polymer (PGFRP) composites, utilizing a representative volume element (RVE) model that incorporates sinusoidal waviness to simulate the behavior of PGFRP with fiber waviness defects. The simulation analysis provided insights into the average stress-strain relationships and equivalent stiffness of the material under various loading conditions. Mechanical performance experiments were conducted on PGFRP under different loading scenarios, and the experimental results were compared with the simulation outcomes to validate the accuracy of the predictive model. The model was employed to investigate the effects of fiber waviness ratio and waviness content on the stiffness of PGFRP. The findings indicate that the fiber waviness ratio significantly impacts the overall stiffness of PGFRP, with a notable decrease in the longitudinal Young's modulus observed when the waviness ratio exceeds 0.02. Specifically, when the waviness ratio reaches 0.1, the longitudinal elastic modulus decreases by 16.7%, and the rate of change of the elastic constants accelerates with increasing waviness ratio. Similarly, the influence of waviness content on the material's longitudinal stiffness is substantial. At a waviness content of 1.0, the longitudinal elastic modulus decreases by 15.2%. Moreover, as waviness content increases, the rate of change of the elastic constants gradually diminishes, leading to significant variations in material stiffness with increasing waviness content.