Abstract: Co-precipitation method was applied for grafting magnetic Fe₃O₄ particles on carbon nanotubes. In order to improve the interlayer properties of carbon fiber reinforced polymer (CFRP), the magnetic carbon nanotubes (Fe₃O₄-MWCNTs) were aligned on the surface of carbon fiber by spraying process after exposure to magnetic field to form ‘carbon fiber-aligned carbon nanotubes-resin’ interface, and were fixed by spraying the resin. Aligned Fe₃O₄-MWCNTs-reinforced CFRP with excellent interlaminar properties was prepared by vacuum assisted resin infusion (VARI) molding. The test results show spraying resin plays an important role in consolidating and improving aligned spraying process. Compared with non-magnetic spraying process, when the mass fraction of Fe₃O₄-MWCNTs is 0.3wt%, the mode I interlaminar fracture toughness (G_IC) increases by up to 37.7%. The main toughening mechanisms, which are pull-out and rupture of Fe₃O₄-MWCNTs aggregates, plastic deformation and plastic void growth of resin, are revealed by the fracture surface morphology. The research provides a new idea and method for interface modification of CFRP by adding Fe₃O₄-MWCNTs with controlled aligned behavior.