In order to achieve high precision 3D measurement of small objects, a set of 3D shape measurement system based on structured light illumination is constructed in this paper. The phase coding algorithm, the calibration algorithm of telecentric camera and the calibration algorithm of projector used in this system are investigated. First, the coordinate of feature points of two-dimensional planar target is obtained by edge extraction algorithm, and an improved Zhang's calibration algorithm is used to complete the calibration of the telecentric camera, and the mapping relationship between camera pixels and projector pixels is obtained by using phase encoded structural light. Then, the mapping relationship enables the projector to capture the position information of feature points, and then complete the calibration of projector. Finally, based on stereo vision model, the object is reconstructed in three dimensions. The measured results show that the calibrated measuring system has a field of view greater than 2 000 cm², the measurement accuracy of full field of view is about 32 μm, and the measurement accuracy of center field of view is 10 μm. It has good stability and repeatability, and can meet the requirements of most industrial testing applications, having a broad application prospect.