Increasing the imaging depth of frequency domain optical coherence tomography (FDOCT) is a key to expand its applications. The method of increasing the imaging depth of FDOCT which is based on the interpixel shift technique is investigated. The principle of the interpixel shift technique is discussed, and the relationship between theoretical maximum imaging depth of FDOCT and the pixel number of charge coupled device (CCD) is elucidated. Then the point spread function (PSF), imaging experiments of five-layer cover glass as well as the vivo imaging experiments of fingers are carried out to demonstrate the effect of interpixel shift technique on the enhancement of imaging depth. The imaging experiments of fingers show that the actual imaging depth increases to 1.98 and 1.12 times after using pixel shift technique in an OCT system with a 256-pixel CCD or a 512-pixel CCD, respectively. The Matlab software simulation validation method provides reference for the FDOCT system on the choice of the pixels of CCD.