In inertial confinement fusion (ICF) experiments, high-density carbon (HDC) is being evaluated as an alternative to the current point-design ablator material (glow discharge plasma) due to its high density and optimal opacity, which leads to a higher energy efficiency and implosion stability. Chemical vapor deposition–coated HDC capsules have a near-perfect surface figure but a microscopically rough surface, so polishing is needed to achieve the required nanometer surface finish. Herein, HDC capsule polishing is investigated with modified four-cup-type polishing technology. The surface morphology, microstructures, and wall thicknesses of the polished capsules were examined by multiple techniques, such as an optical microscope, scanning electron microscope, X-ray radiography, and so on. The results show that the HDC capsules can be polished to a surface roughness less than 15 nm and a wall thickness nonuniformity of about 0.5 μm. The Raman spectra indicated that four-cup polishing had no obvious influence on the original surface crystallinity and phase composition of the HDC capsules. The crystallographic of the HDC capsules with different four-cup polishing times had no deterioration. This work plays an important role for the application of HDC capsules in ICF research.