Abstract: The wetting agent containing carbon nanotubes (CNTs) and deionized water was prepared, in which carbon fibers were infiltrated, and then dried. The effects of CNTs content and infiltrating process on CNTs distribution on the surfaces of carbon fibers were studied by means of SEM and AFM. The influence of CNTs wetting agent on the interface bonding property of carbon fiber/epoxy resin and the mechanism were investigated using single fiber fragmentation test. The results show that T700 and T300 carbon fibers can be coated with CNTs after infiltrated in the wetting agent and the content of CNTs on the surfaces is higher using the wetting agent with higher content of CNTs. For the wetting agent with low content of CNTs, the method of increasing infiltrating times is an effective way to increase the CNTs content and roughness of carbon fiber surfaces. The interface bonding strength of carbon fiber/epoxy resin is obviously improved by 35.8% at maximum after carbon fiber being infiltrated in the CNTs wetting agent, resulting from the enhancement of mechanical interlocking at the interphase regions.