Abstract: High concentration nano-silica slurry is a common abrasive for wafer chemical mechanical polishing. It is key technology to keep the dispersion stability of high concentration nano particle suspension system in slurry. It is usually characterized by Zeta potential, but there are still many problems in Zeta potential measurement of high concentration slurry. The Zeta potential of high concentration nano-silica slurry was measured by electrophoretic light scattering method and the feasibility of this method was studied. The results show that the mother solution equilibrium dilution method, which can maintain the chemical equilibrium between the particle surface and the solution, is the basis for accurate measurement of Zeta potential of high concentration samples. For the dilution of high concentration slurry which is difficult to obtain the supernatant, the sample preparation method of centrifugation to reduce the particle concentration can quickly and accurately obtain the Zeta potential measurement results. In the same dispersion system, the measured Zeta potential is independent of the particle size in the dispersion system.