Anaerobic digestion (AD) is a sustainable biotechnology, which has been applied in the treatment of organic waste. Refractory phenolic compounds, as the main toxic substances in the anaerobic digestion process, usually undergo complex and slow degradation. The addition of hydrochar and co-substrates has been found to effectively enhance the efficiency of phenol anaerobic digestion. This study investigated the simultaneous addition of hydrochar and co-substrates and its impact on anaerobic degradation of phenol. Results indicated that the addition of hydrochar and co-substrates reduced the lag phase of phenol anaerobic digestion, shortening it from 77.5 days in the control to 24.6~59.3 days. When hydrochar and co-substrates were added simultaneously, the maximum methane production rate (Rm) increased from 3.53 mL/d to 4.86~6.80 mL/d. However, when only co-substrates were added and the concentration was too high, it hindered the stimulation of Rm. The optimal concentration for glucose co-substrate addition was approximately between 1.0 and 2.0 g/L. A high concentration of glucose in the environment might enrich other competitive microorganisms, leading to the inhibition of benzoic acid-degrading bacteria and acetate-consuming methane-producing bacteria. Hydrochar also promoted the enrichment of benzoic acid degraders, but the influence of glucose co-substrate concentration on community composition was mitigated in the presence of hydrochar. This study utilized hydrochar and co-substrates to enhance anaerobic degradation of phenol, providing a novel approach to improve the efficiency of phenol anaerobic digestion.