A method was developed for the quantification of the optical purity of L-phenylalanine with chiral stationary phase.L-phenylalanine and D-phenylalanine were separated on SUMICHIRAL OA-5000 column (250 mm × 4.6 mm, 5 μm), with a mobile phase consisted of copper sulfate (1 mmol/L)-isopropanol (87:13, volume/volume).The wavelength was 254 nm.The resolution of L-phenylalanine and D-phenylalanine was 4.615.The retention time of L-phenylalanine and D-phenylalanine was 10.383 min and 16.067 min resp.This method was simple and had great repeatability, and it could be used to determine the optical purity of L-phenylalanine in industry.