The invention discloses a method for reducing the content of free phenol in a phenolic resin and a cleaning preparation method of the phenolic resin. By adopting the method, the content of free phenolis effectively reduced through alkali washing, influence of the free phenol upon properties of resins and damage upon the environment and human bodies can be avoided, the operation is concise, efficient and low in cost when being compared with a conventional treatment method, the property of the resin is not affected, and the method is convenient to implement. In a resin preparation process, organic solvents, water, inorganic salts and phenol are all sufficiently recycled, circulation use is achieved, the process is clean and environmentally-friendly, great economic and social meanings can beachieved, the obtained phenolic resin has excellent adhesiveness and adhesiveness durability, is a very good tackifying resin and is particularly suitable for being used as a rubber use long-lastingtackifying resin applicable to manufacturing and production of tires.