The single-walled carbon nanotubes (SWCNTs) were non-covalently modified and combined with epoxy resin (EP) to prepare SWCNTs/EP composites. The nanomodified epoxy resin was then compounded with carbon fiber (CF) to fabricate CF/SWCNTs/EP multiscale composites, with subsequent investigation of their structure and properties. Results demonstrate that non-covalent modification improved the dispersion of SWCNTs in the EP matrix. When the mass fraction of SWCNTs reached 0.005%, the composite exhibited significant enhancements. The flexural strength and modulus increased by 29.2% and 46.1% respectively, the impact strength improved by 47.9%, and the tensile strength rose by 58.9%. Scanning Electron Microscopy (SEM) analysis revealed the bridging reinforcement mechanism of SWCNTs within the matrix. The thermal properties of EP were also enhanced through SWCNTs incorporation. Using the solution impregnation method, CF/SWCNTs/EP multiscale composite laminates showed 22.5% and 32.8% improvements in flexural strength and modulus respectively at 0.005% SWCNTs loading, along with 15.2% enhancement in interlaminar shear strength and improved interfacial bonding between matrix and fibers. Carbon fiber pressure vessels fabricated via wet winding process demonstrated that the CF/SWCNTs/EP modified vessels achieved approximately 15.5% higher burst pressure compared to conventional CF/EP vessels.