A new technique for identification of two aromatic isomers between 2-hydroxy benzoic acid (2-HBA) and 3-hydroxy benzoic acid (3-HBA) was finalized by using their perturbation effects on a Briggs-Rauscher (BR) oscillator, in which a tetraazamacrocyclic Ni complex, [NiL](ClO4)(2) was used as catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethy1-1,4,8,11-tetraazacyclotetradeca-4,11-diene. By putting two isomers into this BR oscillator, the 2-HBA caused a decrease in potential (amplitudes), an increase in the period of oscillation (AT) and a decrease in number of the oscillation cycle (n) while no influences of 3-HBA on the BR oscillation were observed. Hence, these two aromatic isomers of hydroxy benzoic acid (HBA) were identified in the range from 1 x 10(-5) to 2.2 x 10(-4) mol L-1. Reaction mechanism of BR has been proposed with reference to the NF and FCA models. An explanation of perturbation mechanism for the BR is that, only 2-HBA reacted with IO2 to form 1,2-quinone while the 3-HBA didn't.