Abstract: Aim To study a new method so as to replace the fluorescence agent by the ordinary tracer in the water tank experiment. Methods The image processing was used to analyse the grey scales of three color primaries. Results The corresponding relation between the concentration of the pume modeled with convenient color element solution and the grey scale of the image was obtained by means of DEC image station, and the linear corresponding coefficient was 99 4%. Conclusion The new method proved available based on a set of water tank experiment.