Traditionally, gear tooth profile is measured by coordinate measurement machines using mechanical probe scanning, which is very time consuming. Therefore, normally only a few lines are scanned across the gear tooth surface, which often do not faithfully represent the whole tooth surface profile. In this paper, a phase-shift optical triangulation technique is applied to the gear profile measurement, which has the advantages of redundant information, speed and non-contact nature. When examining a 2 cm2 area, comparative measurement accuracy better than 1 micrometers and resolution about 0.1 micrometers has been successfully demonstrated with the system; this corresponds to a 5 by 10-5 relative accuracy. The measurement result from the optical system displaced good correlation with those form a mechanical probe on a coordinate measurement machine. A few teeth/second measurement speed can also be expected. Different factors to effect the measurement accuracy are discussed, and the possible solutions are provided.