Tyrosine is a monohydrolic aromatic amino acid and DOPA is a tyrosine derivative containing dihydroxy group. DOPA can be synthesized from tyrosine by enzymatic reaction. The separation and quantitative determination of each component are very difficult in the reaction mixture. In the present study, two wavelengths giving maximum absorbance difference of each amino acid were determined using UV/VIS spectrophotometer by wavelength scanning and simple assay method was developed for the analysis of the reaction mixture of tyrosine and DOPA by measuring absorbances of reaction mixture. This method can be simply used for the analysis of the tyrosine and DOPA mixture because it does not require and procedure for the pretreatment of the reaction mixture.