Effects of the electrochemical oxidation on the mechanical properties of UHMCFs and their reinforced epoxy composites were furtherstudied. When the current density increased from 0 to 1.0 A/m2, a sharpdecrease in the tensile strength of UHMCFs occurred due to the chemical etching and oxidation. However, the tensile strength of UHMCFsgradually increased with the current density more than 1.0 A/m2,which possibly resulted from the chemical crosslinks between graphitelayers of UHMCF surfaces. The ordered graphite structure were destroyed in the electrochemical oxidation, as a result, the tensile modulus of UHMCFs continued decreasing as the electrochemical oxidation progressed. The ILSS values of UHMCFs reinforced compositesgradually increased due to increased interfacial chemical bonding afterthe electrochemical oxidation