Abstract: The self-developed carbon fiber wide-spreading equipment was used to pre-dip 12K carbon fiber(CF) into wide CF/epoxy(EP) prepreg with 0.02 mm and 0.10 mm thickness, and the unidirectional laminate of 1 mm thickness was fabricated by molding process. The integrated system including universal testing machine, acoustic emission device and high-speed camera was used to test the tensile strength, the damage inside the sample during loading and the macroscopic morphology of the sample during fracture failure. The tensile fracture morphology was observed by SEM. The super-depth microscope and metallographic microscope were used to observe the arrangement of CF in CF/EP composite prepreg and unidirectional laminate to characterize the influence of CF and EP distribution on the tensile properties of CF/EP composites during thinning. The results show that the CF is more uniform in the thin CF/EP composite prepreg, and the scale of the inter-layer resin enrichment zone in the CF/EP composite unidirectional laminate is much smaller than the laminate made of thick CF/EP composite prepreg. The tensile strength of CF/EP composites sample is increased by 15%. The delamination and splitting phenomenon of the laminate made of thin CF/EP composite prepreg is reduced in the macroscopic fracture morphology, and the clustering property is enhanced. No penetration cracks across the cross section are found in the micro fracture morphology of laminate made of thin CF/EP composite prepreg.