Carbon/ glass fibre-reinforced plastic (C/GFRP) offers advantages in engineering applications due to its low cost. However, the mechanism underlying the evolution of damage in C/GFRP under tension remains unclear. Advanced in-situ micro X-ray computed tomography (µCT) is a useful method for investigating the damage evolution of fibre composites. In this study, two tensile specimens, carbon fibre reinforced plastic (CFRP) and C/GFRP, were prepared, and in-situ µCT scanning was performed at different points during the tensile process. To quantify the voids, examine the fracture morphology, and investigate the void volume fractions, three-dimensional (3D) models were constructed while employing an image reconstruction algorithm. Finally, digital volume correlation (DVC) was employed to study the 3D strain fields. The results suggest that C/GFRP exhibits a higher initial void volume ratio and a faster rate of damage evolution. The 3D strain field and stress concentration area can be used to predict the precise location where the specimen would fracture.