The invention relates to a cardanol modified nitrile-based phenolic resin adhesive and a preparation method thereof, and belongs to the technical field of adhesives. In order to solve the problems oflarge brittleness, low joint strength, high viscosity and poor technological properties of existing phenolic resin, the cardanol modified nitrile-based phenolic resin adhesive is provided. The cardanol modified nitrile-based phenolic resin adhesive comprises nitrile-based phenolic resin and cardanol nitrile-based resin. The preparation method of the cardanol modified nitrile-based phenolic resin adhesive comprises the steps that the cardanol nitrile-based resin is prepared, phenolic resin is prepared, the nitrile-based phenolic resin is prepared, and the cardanol nitrile-based resin is used for modifying the nitrile-based phenolic resin to obtain the adhesive. The cardanol modified nitrile-based phenolic resin adhesive and the preparation method thereof have the advantages that the advantages of the low viscosity and high temperature resistance activity of the cardanol nitrile-based phenolic are utilized, the cardanol nitrile-based resin is used for modifying the nitrile-based phenolicresin, which can significantly reduce the viscosity of the nitrile-based phenolic resin while improving the flexibility and bonding performance of the adhesive, thereby improving the processing technological properties of the high-temperature-resistant adhesive and reducing the use quantity of a solvent. The cardanol modified nitrile-based phenolic resin adhesive is an environment-friendly material.