A profile 3D visual measurement system for free-form surface object i s presented in this paper.The system combines stereo vision and phase-shifting grating.Firstly,the mathematical model of the measurement system and its calibration are demonstrated. Then,the theory of phase computation is described deeply.Finally,a novel phas e computation algorithm is proposed to resolve the main problems in current researches.The compa rative experiments are carried out to verify the advantages of our algorithm in aspects of precision and rate.The feasibility and accuracy of the s ystem are also analyzed.Extensive experimental results show that the measurement accuracy of our system is about 0.04mm.