The aim of this study was to quantitatively analyze the diffusion coefficient of material under wave action by the tracer method. An experiment was carried out to record the diffusion process of marine material using a CCD camera. A smooth relative concentration contour and centerline series of a tracer image was obtained using a powerful image processing function provided by MATLAB. The image showed the relationship between concentration contour series and diffusion coefficient of material by means of theoretical analysis. On the basis of this result, the experimental measurement of the diffusion coefficient under the combined action of wave and current can be quickly realized.