Abstract: In this work, biomolecule, L-phenylalanine, was used to modify electrode for detection uric acid (UA) in urine. A poly (L-phenylalanine) was prepared via cyclic voltammetry, and the electrochemical behavior and the voltammetric determination of uric acid (UA) on this modified electrode were studied. The results showed that a sensitive oxidation peak was observed at about 0.43V, which was corresponding to the electrooxidation of UA, on this modified electrode in phosphate buffer solution (pH 5.6). The peak current is well proportional to the concentration of UA in the range of 2.0×10-6 ~ 3.0×10-4mol/L with a detection limit of 1×10-6 mol/L. The relative standard deviation for five determinations of 1.0×10-5 mol/L uric acid is 3.0%. The modified electrode is easy to prepare with good reproducibility and it has been applied to the determination of UA in urine with satisfactory results