A sensitive electrochemical sensor based on cobalt oxide decorated reduced graphene oxide and carbon nanotubes (Co3O4-rGO/CNTs) has been successfully fabricated towards nitrite detection. Cyclic voltammetry and potential amperometry experiments were conducted on Co3O4-rGO/CNTs electrochemical sensor to investigate the electrochemical sensing performances. Several important electrochemical sensor parameters have been evaluated for nitrite oxidation, such as pH, modified amounts and mass ratio of electrode modified materials. The measured results shows that the as-prepared gas sensor exhibits a high sensitivity of 0.408 mu A.mu M-1.cm(-2) (0.1 mu M to 8 mM), linearly proportional to nitrite concentrations in the range of 8 mM to 56 mM and a low detection limit of 0.016 mu M. Meanwhile, the Co3O4-rGO/CNTs/GCE sensor also displays excellent anti-interference ability and good long-term stability. Furthermore, the proposed sensor was also applied to determine the nitrite level in real samples with satisfactory recovery, which implies its feasibility for practical application.