Color composition is simple and useful in image enhancing processing

but is always limited by user’s experence. In this paper a metho of choosing color composition is given which is based on chromaticity. The visual sensitivity to color difference between objects on computer VDP can be caculated in all kinds of possible color composition

then the best choice of color composition can be gained. It is very profitable to apply this method to extract interesting information from images. In Huanghe River mouth there are about four kinds of objects such as Yellow Sea water

Huanghe Water

delta Land and seabeach which basicly determine the enviromental changes and influence the oil industry development. Using Thematic images and choosing best color composition has successfully define the boundaries between objects and provides exact data for further studies.