An orthogonal dispersive spectral-domain optical coherence tomography (SDOCT) system based on a spectrometer consisting of a high spectral resolution virtually-imaged phased array (VIPA) and a low resolution diffraction grating is developed. Two-dimensional (2D) dispersion generated by the combination of the VIPA and the grating in conjunction with a 2D CCD leads to an improved performance of the spectrometer. Ultrahigh spectral resolution of 0.002 nm within a free spectrum range of 50 nm is realized, providing the spectrometer with a spectral sampling rate up to ~10(5). The developed SDOCT realizes an imaging depth over 80 mm, which is the longest depth range ever achieved by SDOCT. The increased spectral sampling rate also results in a high signal-to-noise ratio of the SDOCT system. The application of the developed system is further illustrated by quantitative phase imaging of a glass plate and an optical lens.