In Fourier transform profilometry (FTP) for three-dimensional (3-D) shape measurement, in order to obtain the height and phase information of a testing object, two images are needed, i.e. original grating pattern and its deformed grating pattern. Therefore, if the optical system is changed, it is necessary to obtain a new original grating pattern. Such arrangement does harm to fast measurement. For overcoming the shortage, a new method is proposed for obtaining the information of the original grating pattern from its deformed grating pattern. First the information of the original grating pattern is recorded in its deformed grating image. Then its frequency and phase are obtained from the deformed grating image by means of image analysis. Finally the complete original grating image is reconstructed and 3-D shape measurement is relized. The experimental results show that the above method is available.