A concentration measuring system based on DSP video processing was established to monitoring dynamically two-dimensional concentration changes for solution. The refractive index changes of the solution were detected by a Mach-Zehnder interferometer, and the interferometric fringes were recorded by a CCD on site. Finally, a DSP was used to process the video images of interferometric fringes to obtain the solution concentration changes. Furthermore, both the hardware platform and the video-processing algorithm of the system were described in detail. The experimental test indicates that the system can provide quantitative measurement for a single-component solution and a multiple-component solution with one main component change. An experiment on potentiodynamic polarization of the electrode in the H2SO4 solution with a concentration of 0.5 mol/L at 2 mV·s-1 shows that the peak concentration of FeSO4 solution at the electrode/electrolyte interface is (9.2 ± 0.2)×10-3 mol/L when the iron electrode potential is -0.428 V. The system has high precision and strong stabilization in online testing and can be employed in measurement of the concentration changes of the solution in real time.