Abstract: The metnoas or rotating ring-disc electrode(RRDE) ana cyclic voltammetry were used to study the oxidation of cgsteine on heat-treated cobalt tetramethoxyphenyl porphyrin adsorbed on graphite(Co-TMPP/graphite) in solutions of various pH.Experimental results showed that Co-TMPP/graphite exhibits significant catalytic activity for cysteine oxidation in solutions with various pH.The current efficiency of cysteine oxidation on Co-TMPP/graphite in basic media is more than 90%.It was found that the kinetics of cysteine oxidation on Co-TMPP/graphite is a simple irreversible reaction controlled by rate of charge transfer.The standard rate,constants(k°) of cysteine oxidation were calculated and the reaction mechanism of this reaction in solutions of various pH wes discussed.