We developed a 3D spectrum domain optical coherence tomography (OCT) system based on fiber-based Michelson interferometer. The measurable depth of the OCT imaging is up to 3.4 mm for the detection part is of high speed spectrometer with 0.05 mm spectrum resolution. The signal-noise-ratio (SNR) and axial resolution of this OCT system are experimentally found to be 51 dB and 8.5 m,respectively. A 3D OCT image could be acquired in two second owing to the fast A-scan rate (up to 10×103 line/s). Using 3D OCT technology,the images of biology tissue such as retina are shown more intuitive and precise.