A novel method for the three-dimensional (3-D) object recognition based on modulation analysis is proposed. Two orthogonal gratings with equal interval are vertically projected on an object surface,and the measured object is placed between the focusing planes of the two gratings. Then the image of orthogonal grating modulated by the object height can be obtained by a CCD camera from the same direction,and the object height information is encoded in this image. They are processed by the operations consisting of performing the Fourier transform,spatial spectrum analysis,so the fundamental spectrum in two directions can be obtained. Then the recognition parameter (the sum of the intensity of each fundamental spectrum) is calculated. The values of recognition parameter are treated as a point in the recognition space. If the shape of object is different,the values of recognition parameter are also different. The different objects will be shown in the different positions because of the deference of the values of recognition parameter. Both computer simulation and experimental results are presented in support of the proposed idea.