The design and optimization for lens group in spectral domain optical coherence tomography (SD-OCT) system is fairly important to improve the imaging quality. The field lens in sample arm and the focus-ing lens in spectrometer are designed based on Zemax, and the imaging quality is evaluated according to spot diagram and wavefront map. The results show that the field lens can provide ideal imaging quality and good lat-eral resolution. And the focusing lens in the spectrometer makes the size of focal spot smaller than the pixel width of CCD to avoid the interference in each pixel of CCD. In this way, we observe considerable improvement in the resolution of the spectrometer.