The early detection and treatment of pathological change tissue has long been a medical priority. Optical coherence tomography (OCT) is a new kind of noninvasive cross- sectional imaging technique. In this paper, experimentally we set up the first OCT system in China that can be obtaining 2D image of biological samples. OCT performs optical ranging in tissue by use of a fiber-optic Michelson interferometer with a low illuminating source, a tunable mode-locked Ti:Sapphire femtosecond pulse laser source, with center wavelength of 830 nm. A matching length of single- mode optical fiber wrapped around a piezoelectric modulator is placed in the reference arm for phase modulation. The properties and experimental results of our OCT system are analyzed. We got cross-sectional images of animal tissue samples. The OCT image of a mouse nephridium cortex tissue is agreed with the histological images. On the other hand, mouse brain (animal model of cerebral embolism) pathological changes tissue and normal tissue can be discriminated. The blood rheology characteristic of brain blood vessel block is discussed. It shows that this technique holds promise as a potential tool for the tissue diagnosis.