Optical coherence tomography (OCT) has become an important medical imaging modality. However, low penetration depth limits its application. Therefore, the optical scanning probe plays an important role in OCT systems for clinical applications. This article reviews OCT methodology and the mechanisms of an optical scanning probe. Recent developments of OCT probe and related clinical applications are summerized. Various OCT probe techniques (e.g., side imaging and forward imaging) have been used for measuring optical biopsy of various tissues. OCT probes for early diagnosis applications should be developed and combined with functional OCT modalities, such as Doppler OCT and polarization-sensitive OCT, to provide more information for diagnosis.