Blanc bromomethylation-dehydrobromination is proposed to synthesize isotropic pitches with superior spinnability, utilizing refined coal tar pitch as the feedstock. This strategy involves introducing bromomethyl functional groups into pitch molecules through the Blanc bromomethylation reaction. In the subsequent process of dehydrobromination, methylene bridges generate between neighboring aromatic molecules. The pitch precursor prepared by this method not only displays an increased level of oligomerization and pitch yield, but also exhibits a more linear molecular structure compared with that produced through purely thermal polycondensation. The enhanced linear molecular configuration contributes to the improved spinnability of the pitch precursor and the oxidation reactivity of its derived fiber. Furthermore, the tensile strength of the resulting carbon fibers rises with an elevation in the amount of polyoxymethylene, and it exhibits the trend of an initial growth followed by a subsequent decrease as the stabilization temperature escalates. The carbon fibers obtained from the pitch prepared through thermal polycondensation present a low Young’s modulus of 24 GPa and a low tensile strength measuring of 456 MPa. In contrast, carbon fibers derived from the pitch synthesized via Blanc bromomethylation-dehydrobromination exhibit superior mechanical performance, offering Young’s modulus and tensile strength of 58 GPa and 1210 MPa, separately.