A new field experimental method of d etermining unsaturated soil hydraulic properties is proposed. In this method these properties are assumed to be represented by van Genuchten' s closed-form expressions. Unknown parameters of this model are identified by Genetic algorithms (GA) incorporating finite element analysis of transient axisymmetric seepage flow. GA are search algorithms based on the mechanics of natural selection and natural genetics. They have become a popular global optimization method. A-ponded singlering infiltrometer technique, such as the Guelph Pressure Infiltrometer is performed. Simultaneously the measured change of soil water content with time and cumulative inflow data are used to identify unsaturated soil hydraulic function parameters. The advantage of the proposed method is that it allows estimation of the unsaturated soil hydraulic parameters by quite simple in-situ permeability test data. The utility of our proposed method is demonstrated by using a numerical model and experimental data for Tottori dune sand.