This study presents a new strategy by integrating surface-initiated atom transfer radical polymerization (SI-ATRP) with bioinspired polydopamine chemistry to prepare well-defined glass fiber/polymer composites. First, a homogeneous PDA layer, which served as a favorable platform facilitating ATRP initiator anchoring, was deposited onto the glass fibers. Controlled growth of poly(glycidyl methacrylate) (PGMA) brushes from the glass fibers was then performed using the initiators for continuous activator regeneration (ICAR) ATRP method. PGMA brushes with defined structure, grafting density (5 wt % to 25 wt %), and good preservation of chain-end functionality could be obtained by reducing radical initiator ratio and using a high dilution strategy (solvent:monomer = 10:1 (v:v)); and a narrow distribution of molecular weight (PDI <= 1.2) could be attained within reduced polymerization time. Laccase, as an enzyme model, was then covalently immobilized to the glass fiber/PGMA composites. The developed biocomposites showed improved enzymatic stability and enhanced catalytic activity toward the degradation of 2,6-dimethoxyphenol.