Abstract: A silane hybrid sol was synthesized by a certain percentage of methyl triethoxysilane (MTES), tetraethyl orthosilicate (TEOS), p-toluenesulfonic acid (PTSA), γ-aminopropyl triethoxysilane (APS) and absolute ethanol via a sol-gel process. An aqueous solution of polyether waterborne polyurethane (WPU) and silane hybrid sol were mixed in a certain proportion to prepare the aqueous sizing agent for carbon fiber. The effects of different ratio for average particle size and stability of the sizing agent were investigated.The results show that the average particle diameter of sizing emulsions is 99.94 nm when the aqueous polyurethane concentration is 0.02 g/mL. And sizing possess narrow particle size distribution and good stability. Adopting dip-coating method to treat carbon fiber surface with the prepared sizing agent, the monofilament tensile strength of the sized carbon fiber increases by 4.45% than the commercial carbon fibers, and increases by 11.04% than unsized carbon fiber; The interfacial shear strength of treated carbon fiber/epoxy resin composites increases by 13.74%.