In this work, Co3O4 nanoparticles (NPs) with an average diameter of about 30 nm were synthesized using MOFs as a template. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) investigation showed that Co3O4 nanocrystals embedded in mesoporous graphitic carbon layer/multiwalled carbon nanotubes (MWCNTs) uniformly. The structure of the final nanocomposite (denoted as Co3O4@C-MWCNTs) was further confirmed by X-ray diffraction (XRD), Raman spectra and Brunauer-Emmett-Teller (BET) techniques. As a result, electrochemical study demonstrated that the Co3O4@C-MWCNTs modified glassy carbon electrode exhibited excellent electrochemical activity toward the reduction of O-2(-). with a super wide linear range from 5.00 x 10(-12) to 1.00 x 10(-4) M and very low detection limit (LOD) of 1.67 x 10(-12) M (S/N = 3). Importantly, three kinds of stimulants were selected to monitor the flux of O-2 - released from living cells. By using phorbol 12-myristate-13-acetate as optimal stimulus, the novel non-enzymatic O-2 (-) sensor can detect O-2. (-) release from cancer cells, which has the great potential application in clinical diagnostics to assess oxidative stress of living cells.