Co3O4 nanoflakes were successfully prepared using a thermal decomposition of precursor approach. The precursor nanoflakes are synthesized by a facile chemical precipitation method. Magnetic measurements reveal that the as-prepared Co3O4 particles exhibit weak ferromagnetic properties. In addition, the prepared Co3O4 nanoflakes electrode was then applied to study the electrocatalytic oxidation and reduction of hydrogen peroxide (H2O2). The results also demonstrate that Co3O4 nanoflakes have great potential in sensor and biosensor applications. The catalytic activity of Co3O4 nanoflakes on the thermal decomposition of ammonium perchlorate (AP) also has been studied. Results show that Co3O4 plays a catalytic role on the thermal decomposition of AP.