The invention discloses a grating compacting device for stereo projection imaging and the method. The device comprises an enlarging-printing platform and a photohead. Compaction mechanisms are arranged on two sides of the enlarging-printing platform; a wind suction port is formed on the enlarging-printing platform; a tuyere is arranged on the photohead; when the whole device is at work, through the wind power of the tuyere, a grating is caused to keep close to a photographic paper, so that the photohead can finish projection sensitive imaging; and through the photohead, mobile projections areconducted on multi-angle images shot by a stereo camera for a plurality of times, thereby causing a stereo image to be compound-imaged, and further completing a mosaics projection photosensitive imaging effect.