Theoretical model of an achromatic phase shifter based on a rotating half-wave plate and its implementation in a full-field optical coherence tomography (OCT) system are proposed for rapid and high-resolution OCT imaging. The phase shifter that is almost independent of the wavelength over a broad range can provide phase shift at eight times of rotating angle of the half-wave plate. Conventional monochromatic phase-shifting algorithms can thus be adopted without systematic errors. Numerical analysis on phase shifting error and amplitude ratio between orthogonal polarization components versus wavelength over a range of 240 nm for nominal phase shifts required for the revised Carré algorithm and three-step phase-shifting algorithm respectively is conducted. The results demonstrate increased phase shift error and increased fluctnation of amplitude ratio for larger nominal phase shift. The full-field OCT system with the proposed achromatic phase shifter has several advantages compared with previous system.