The invention provides an optical tomography system based on a scanning galvanometer, and the system employs the elements: a visible laser source, an MEMS two-dimensional scanning galvanometer, a diffuse reflection curved surface, a diffuse film, and a linear array CCD camera. The system employs the following steps for the reconstruction of the shape of an opaque object: adjusting the vibration parameters of the MEMS two-dimensional scanning galvanometer through programming, and enabling the reflected light of the MEMS two-dimensional scanning galvanometer to form a 180-degree continuous scanning track on the diffuse reflection curved surface; placing the light-transmitting diffuse film behind the object, wherein there is a shadow region on the diffuse film because the object is opaque; carrying out the high-speed photographing of the diffuse film through the linear array CCD camera, and obtaining the original light intensity data; processing the original data, calculating the actual space position of the shadow region, obtaining two boundary lines of the object, obtaining a plurality of boundary lines of the object through 180-degree scanning, and completing the reconstruction ofthe shape of the opaque object. The method achieves the 180-degree continuous scanning of the object, improves the scanning speed, increases the obtaining quantity of the original data, and is good inapplication prospect.