The present invention provides a method for preparing phenolic resin adhesive with by-products in cresol production. The method comprises: using by-products in the cresol production as raw materials; synthesizing modified phenolic resins through a chemical reaction by using valid functional groups of compounds in the by-products; and preparing phenolic resin adhesive with acceptable performance by compounding phenolic resins with a tackifier and a curing agent in the solvent. The study shows that the phenolic resin adhesive provided by the present invention has the advantages of good bonding performance, low cost and oxidation resistance. Product quality reaches the national profession standard. More importantly, according to the present invention, all the by-products in the cresol production are used without being treated, the method has the features of being simple in production process, mild in reaction condition, stable in operation, high in feasibility, low in comprehensive cost and significant in economic benefits. The method realizes the real zero emission of wastes from the phenolic industry, fundamentally solves the environmental pollution caused by wastes, and achieves the objective of changing wastes into valuables.