An on-line three-dimensional measuring method based on speeded up robust features algorithm is proposed. Only one fixed sinusoidal grating is projected onto the moving measured object to guarantee the fringe direction perpendicular to the moving direction. While the object moves at the same spacing, the corresponding deformed patterns are captured by the CCD camera respectively. Then the background patterns can be extracted from the corresponding captured deformed patterns. With the aid of Speeded Up Robust Features（SURF）feature points matching algorithm on the background patterns, a group of equivalent phase shifting deformed patterns with the same shifting phase can be cut out. So the 3D surface of the online moving object can be reconstructed. The experimental results show the feasibility and effectiveness of the proposed method. Moreover, compared with the online Fourier Transform Profilometry （FTP）method, its average absolute error is less than one-half of that of the online FTP and its root mean square error is less than one quarter of that of the online FTP.