We demonstrate the feasibility of a four-focus switch Fourier-domain optical coherence tomography system for whole eye segment imaging, and in vivo visual axis parameter (VAP) measurement. In this study, we use two rotating disks to switch the focus position synchronously, to expand the detection depth range. Three parallel glass plates of different thicknesses are placed on a rotating disk along the path of the detection beam, so as to switch the focus position of the probing beam from the cornea, the anterior and posterior of the lens to the retina. On the other synchronously rotating disk, the light path of the reference arm can simultaneously extend the detecting optical path to match the probing beam. This multistage focusing method can make the probing beam completely focused on each segment of the human eye during the course of signal collection. Subsequently, we measured VAP several times, and the results show that our four-focus switch FD-OCT system exhibits good repeatability. In conclusion, we prove theoretically and experimentally that the proposed four-focus switched FD-OCT system can realize whole eye segment imaging and VAP measurement, including central corneal thickness, anterior chamber depth, lens thickness, and axial length. Our method will be beneficial for measurements in ophthalmology.