The grating projection method is used for the three-dimension profilometry measurement. But disconnected phase can′t be unwrapped when shadows exist in the grating stripes due to the steps on the object. In order to resolve the problem, the object is put on a precise rotary platform to achieve the clear grating-modulated image of the object by taking two images and mosaicing them together. In the image mosaic, the conception of contrast among successive regions is introduced. Where the contrast of the successive regions is the greatest, the place is regarded as the boundary of the black and white. The place of the boundary of the middle block can be accurately located and the image is mosaiced. At last, Fourier transform profilometry based on dualfrequency grating is used to realize the three-dimensional profilometry reconstruction. The result indicates that the method is simple and accurate, and can successfully solve the problem of the threedimensional profilometry reconstruction of the object with steps.