A facile yet effective chemical vapor deposition (CVD) method to prepare carbon nanomesh (CNM) with MgAl-layered double oxides (LDO) as sacrificial template and ferrocene as carbon precursor is reported. Due to the combined effect of the LDO template and organometallic precursor, the as-made hexagonal thin-sheet CNM features a hierarchical pore system consisting of micropores and small mesopores with a size range of 1-6 nm, and a great number of random large mesopores with a pore size of 10-50 nm. The density, geometry, and size of the pores are strongly dependent on the CVD time and the annealing conditions. As supercapacitor electrode, the CNM exhibits an enhanced capacitance, high rate capability, and outstanding cycling performance with a much-shortened time constant. The excellent capacitive performance is due to the presence of the large mesopores in the 2D CNM, which not only offer additional ion channels to accelerate the diffusion rate across the thin sheets but also help to make efficient use of the oxygen functional groups at the edges of large mesopores to increase the pseudocapacitance contribution.