Relating to devices and methods for carbon fiber interfacial modification, the invention provides a device and method for preparation of continuous carbon fiber with carbon nanotubes growing on the surface. The invention aims to solve the problem that continuous modified carbon fiber cannot be obtained through existing modification of carbon fiber with carbon nanotubes. The device comprises a quartz tube, a head-end sealing plug, a tail-end sealing plug, front drawing rollers, back drawing rollers, a micro-injection pump, a hydrogen generator, an argon bottle, a gas mixing apparatus, a tail gas treatment device, an exhaust pipe, a heating jacket and a sealed bin. The micro-injection pump and the gas mixing apparatus are both connected to the quartz tube, and the heating jacket is disposed outside the sealed bin. The method consists of: passing a carbon fiber tow through the front drawing rollers, the back drawing rollers and the quartz tube and conducting tensioning, introducing argon into the quartz tube to perform purification, then introducing the mixed gas of hydrogen and argon into the heated quartz tube, then dissolving ferrocene into a solvent and then introducing the product into the quartz tube, and depositing carbon nanotubes on the surface of moving carbon fiber so as to obtain continuous carbon fiber with carbon nanotubes growing on the surface. And the continuous carbon fiber with carbon nanotubes growing on the surface can be used as a reinforcement in composite materials.