To correct the color separation of a large format CCD camera, this paper researches the internal structure of the CCD, analyzes the reasons of three color separation of multi-linear-array CCDs and proposes a new correction method to cache three-channel data separately. Then, it establishes the first high-speed tri-CCD large format scanner domestically. On the basis of the internal process structures of the tri-CCD, this correction method caches and restructures the three-channel data in hardware separately, and restores the true color. The theoretical analysis and practical application results show that three-color separation phenomenon has been greatly reformed after treated, and three-channel color is not separation in 1 200 DPI. In 600 DPI, the scan speed of the scanner produced by our team has been up to 5.08 cm/s, and it only takes 30 s to scan a A0 size drawing. Furthermore, the splicing error of the image after scanning will be superior to ±2 pixels。