The electrophoretic mobility of a charged particle can be determined using the electrophoretic light scattering method. To accurately determine the particle's Zeta potential from the mobility requires the use of Henry function. An optimal expression for Henry function can be fitted by using the least squares algorithm. The thickness of the electric double layer in different concentrations and different types of electrolyte can be calculated using the Gouy-Chapman-Stern double layer model. An accurate value of ka is obtained, here k -1 is the thickness of the double layer and a is the particle radius. The value of ka can be used in the optimal expression to determine an accurate value of Henry function. The particle's Zeta potentials for four different concentrations are measured using this approach. The experimental results show that the optimal Henry function can be used to improve the calculation precision of particle's Zeta potential, and the relative error of the calculation results is less than 1.0%.