Objective To address the limitation of spectral overlap interference in the rapid detection of 3,4-dihydroxyphenylethanol (DHPET) within the 4-hydroxyphenethyl alcohol (HPET) catalytic system using traditional ultraviolet spectrophotometry.Methods To overcome the insufficient specificity of existing methods, a rapid spectrophotometric detection method based on Fe³⁺ coordination modulation was proposed. Through bidentate chelation between Fe³⁺ and the catechol group of DHPET, the characteristic absorption spectrum was induced to undergo a bathochromic shift to 760 nm, significantly distinguishing it from the weak coordination response of monophenolic compounds.Results After optimization, the method exhibited a linear range of 3~100 mmol/L (R²=0.998), a detection limit of 0.709 mmol/L, and precision with RSD<2%, meeting the requirements for real-time monitoring in industrial catalytic systems.Conclusion The molecular mechanism of enhanced selectivity through bidentate coordination is practical in enzymatic catalytic systems, providing a low-cost, rapid analytical tool for the industrial production of DHPET.