A three-dimensional (3D) shape measuring system has been built. In the system, a high-speed digital projection module was developed with a DLP4500 chip and synchronously trigged with a CCD camera. Three different frequencies fringe patterns were projected onto the surface of a tested object in turns and were used to calculate the natural phase distribution, as well as the height distribution of the measured object by phase-shifting algorithm and heterodyne phase unwrapping method. Several practical experiments were carried out some tested samples in a small field of view (8 mm×6 mm). The results show that the system can restore the objects’ (coins for example) 3D shape (~100 μm) with a high accuracy.