The superior electrical conductivity and parallel ion pathways formed by aligned carbon nanotubes (A-CNTs) make them attractive for the nanoporous electrodes of supercapacitors. To achieve high volumetric energy and power densities, the low volume density of the as-synthesized A-CNT (<5%) should be densified. In this paper, we demonstrate a mechanical densification method that allows the density of A-CNTs to be tuned precisely over a broad range while preserving the straight ion pathway between A-CNTs. The supercapacitors fabricated from 40% volumetric fraction (Vf) of A-CNTs as the electrodes with the thickness of 0.8mm exhibit a power density of 25kWL−1 (50kWkg−1), which is much higher than that of the A-CNTs electrodes with similar thickness fabricated by other methods and that of activated carbon electrodes.