Increasing social awareness concerning the design of excellent performance toughening agents to curb the adverse effects of insufficient toughness on the wide range of applications of epoxy resin (EP). Herein, a small amount of sorbitol was doped into carbocyclic inositol as a core monomer, and bisphenol‐A and epichlorohydrin were used to produce epoxide‐terminated hyperbranched polyether by one‐pot preparation method. After that, the prepared polymer was used as modifier to improve the toughness and strength of petroleum‐based EPs. Results demonstrated that after adding the homemade epoxy‐terminated hyperbranched polyether (EHBPE) to the EP, the polyether prepared with the ratio of sorbitol and inositol displayed significant advantages compared with the polyether with monomers using only sorbitol and inositol, respectively. In particular, the impact, and tensile strengths of EHBPE‐IS/EP cured sample with EHBPE‐IS loading at 20% were increased by 197.5%, 139.6%, respectively, compared with those of neat EP. In brief, EHBPE‐IS, a member of the family of EHBPEs, provided a facile method for the preparation of bifunctional modifier for tough and strong EP with promising industrial applications.