Abstract: Blended alkylphenols can be obtained after extraction of medium- and low-temperature coal tar. Since the boiling points of different alkylphenols are close to each other, it is technically difficult and economically disadvantageous to separate them into monomers by distillation. Dealkylation of alkylphenols to phenols allows for efficient utilization of mixed alkylphenols. HZSM-5 catalysts have superior product selectivity for dealkylation of alkylphenols, but suffer from poor stability. Therefore, a hierarchical HZSM-5 catalyst was prepared by introducing mesopores into microporous HZSM-5 catalyst by alkali treatment and used in alkylphenol dealkylation reaction. The effects of mesopore structure and co-feed water on the reaction performance of alkylphenol dealkylation were investigated. The surface structure and properties of the hierarchical HZSM-5 catalysts were also systematically investigated in combination with a series of characterization techniques, and the mechanism of mesoporous structure and water co-feeding on the catalytic alkylphenol side-chain tailoring reaction catalyzed by the hierarchical HZSM-5 catalysts was clarified. The experimental results showed that the presence of mesoporous structure shortens the diffusion path of molecules and enhances the diffusion of reactants and products, thus improving the catalytic performance of HZSM-5 catalyst. At the same time, water inhibited the formation of coke inside the pores through competitive adsorption, thus improving the stability of the catalyst. Hierarchical HZSM-5 catalyst was subjected to 75 h of long- life experiments in the presence of co-feeding water, wherein phenol maintained a 95% selectivity, and no significant decrease in conversion was observed. In addition, a mixture of 4-n-propylphenol and 4-ethylphenol was selected as the reactants to study the catalytic performance of the hierarchical HZSM-5 catalyst for the mixed phenol side-chain tailoring, and the experimental results showed that the phenol product maintained a 90% selectivity within 8 h, which proved that the hierarchical HZSM-5 catalyst was also applicable to the mixed phenol side-chain tailoring reaction.