Abstract: In order to make it easier to identify objects in a radiation image obtained by container inspection system using cobalt-60 source, the method was described for transforming a radiation gray image into a pseudo color image based on the image’s gray characteristic. The radiation image was preprocessed so that pixel grays were mapped to a low range of grays. The colors in a color list were dynamically allocated to different grays according to histogram of the radiation image. The color list was set up according to Ostwald color order system, so that the color display was more identifiable. This method was applied in a container inspection system of a customs and the display effect was very good.