The invention discloses a carbon fiber reinforced montmorillonite modified nylon 6 composite material and a preparation method thereof. The composite material comprises the following raw materials in percentage by mass: 50-85% of montmorillonite modified nylon 6, 10-40% of carbon fiber, 0.5-5% of a compatibilizer, 0.2-0.6% of an antioxidant and 0.5-5% of a lubricating agent, wherein the montmorillonite modified nylon 6 is a montmorillonite nylon 6 complex prepared by in-situ polymerization of nanometer montmorillonite. According to the montmorillonite modified nylon 6 composite material, montmorillonite modified nylon 6 prepared by in-situ polymerization is adopted as a matrix to prepare the carbon fiber reinforced montmorillonite modified nylon 6 composite material, the problem that the material has defects due to the non-uniform dispersion of montmorillonite in the prior art is avoided and the composite material has the advantages of good strength, stiffness, deformation resistance, excellent surface properties and good processing properties.