Micro-structured surfaces such as micro-aspheric lenses/lens arrays and micro-gears are getting increasingly important in industries. A lot of micro-structured surfaces have complicated three-dimensional (3D) profiles with short pitches and large amplitudes (high-aspect-ratio). Some of them also have steep surface slopes. It is difficult, however, to use conventional measuring instruments to measure profiles of such 3D micro-structured surfaces. This paper describes a contacttype displacement sensor for profile measurement of 3D microstructured surfaces. The shaft of the sensor is levitated by airbearings to reduce the contact force between the sensor and the measured surface. A sharp corn stylus is attached at the end of the sensor shaft. A precision glass micro-ball is glued on the top of the stylus shaft. The diameter of micro-ball is under 50 μm. The displacement sensor is also used to measure the profile of a micro gear with a high-aspect-ratio surface profile.