Abstract: It was proposed that tyrosinase was immobilized on the inner membrane taken from bamboo and activated by pentanedial to prepare a detection unit for photometric determination of L-tyrosine. The determination was based on the catalytic action of tyrosinase on the transformation of L-tyrosine to dopa-quinone which was in turn reacted with 3-methyl-2-benzothiazolinone hydrazone (MBTH) to give a chestnut colored additive product having its absorption maximum at 490 nm in a PBS of pH 7.0. Values of absorbance measured at this wavelength were found to keep linear relationship with concentration of L-tyrosine in the range from 5 to 200 μmol·L-1, with its detection limit (3S/N) of 2.5 μmol·L-1. The proposed method was applied to the determination of L-tyrosine in injections of compound amino acids the results obtained were in consistency with the labelled value.