In this paper, with the synergistic effect of C, Co and O elements, and with a one-dimensional carbon nanotube (CNT) as the structure guide agent, a two-dimensional Co3O4 nano-sheet with high catalytic activity was prepared, and its catalytic activity was further improved by adding a manganese element. By controlling the annealing time, a two-dimensional Co3O4-based nano-sheet with a regular arrangement of atoms on the surface was gradually formed during the oxidation process of CNT. Then, the lattice distortion of Co3O4 was caused by doping manganese. The interaction between Mn and Co promotes the cycle capacity of Mn/Co redox pair and the generation of reactive oxygen species, which is conducive to an improvement in catalytic activity. Finally, under different catalytic conditions, the 2D Co3O4-based catalysts all showed stable catalytic performances, among which methane flow rate had a great influence. When the airspeed was controlled within the range of 42,000 mL·g−1·h−1, the methane conversion rate could still reach 90% (450 °C).