Abstract: CMYK transformation and its application in image processing and geoscience studies are briefly introduced in this paper. Its comparison with the conventional methods shows that this method has the advantages of simple calculation and operation and production of high-quality images. Comparative study shows that the merged images produced by the transformation cannot be compared by other methods. In addition, the CMYK transformation also provides a new four-band image composition method and has wide application prospects in respect to remote sensing image processing and integrated processing and display of other kinds of geoscience data.