Nanomaterials as enzyme mimics have received considerable attention as they can overcome some serious disadvantages associated with the natural enzymes. In recently developed Co3O4 nanoparticles as peroxidase mimics, the influence of the crystal plane on the catalytic performance has not been demonstrated. In order to better understand their crystal plane-dependent catalysis, the present study was initiated using three different Co3O4 nanomaterials, nanoplates, nanorods and nanocubes, as model systems. According to HRTEM, the predominantly exposed planes of nanoplates, nanorods and nanocubes are {112}, {110} and {100} planes, respectively. The catalytic activities were explored by using H2O2 and different organic substrates as the substrates of peroxidase mimics, and were investigated in-depth by steady-state kinetics and electrochemistry methods in depth. The results show that the peroxidase-like activity increases from nanocubes to nanoplates, via nanorods. The effect of external conditions such as pH and temperature on the three nanomaterials is the same, which indicates that the difference in their catalytic activities originates from their different shapes. The peroxidase-like catalytic activities of Co3O4 nanomaterials are crystal plane-dependent and follow the order: {112} ≫ {110} > {100}. The three crystal planes have different arrangements of surface atoms, thus exhibiting different abilities of electron transfer, which induce their different peroxidase-like catalytic activities. This investigation clarifies that the peroxidase-like activity of Co3O4 nanomaterials can be enhanced by shape control. These findings show that Co3O4 nanomaterials can serve as catalyst models for designing other catalysts.