The electrochemical behavior of m-NO2C6 H4SO3 Na on Cu electrode is investigated in DMF（TBAP），H2O and DMF/H2O（TBAP） mediaThe working electrode was a Cu electrode，the auxiliary electrode was a large area platinum wire，and the reference electrode was a saturated calomel electrodeIt was shown that the reaction of m-NO2C6H4SO3Na on Cu electrode would undergo two steps in which ArNO2/ArNO-2·was a reversible process controlled by the diffusion of m-NO2C6H4 SO3 Na in aprotic mediumIn protic medium，the electrochemical reduction of m-NO2C6H4SO3Na would undergo two steps of oxidation-reduction reaction of ArNO2/ArNO and ArNO/ArNHOHWhile in mixed medium，due to the hindrance of protonation by DMF，m-NO2C6H4SO3Na was firstly reduced to ArNO-2· and further reduced to ArNHOHThese results could be interpreted by the calculation of qauntum