Abstract: Parameter estimation is the key job of mathematics simulation and calculation,and its most complex problem is the simulation of water movement and contamination transferring in unsaturated soil. On the basis of analyzing movement and transference,the hydrodynamic functions of piecewise-continuous which is suitable for coordinate grid is adopted,and a contamination distributing equation about soluting concentrations in the liquid,solid,and gaseous phases in variably saturated soil is established. The inverse problem mode is adopted to discuss the optimization estimation technique of the model parameters. The Levenberg-Marguardt modification of the Gauss-Newton minimization algorithm is used to calculate iterative problem of the model parameters. The experiment model parameters of one-dimensional soil column and two-dimensional large tilting soil tank are estimated by the method,and the effect of the given parameter and estimation amount on parameter's confidence intervals and forecast result are discussed. The identified and analyzed results shows that the parameter estimation technique is feasible and the forecast result is dependable. The parameter estimation technique is used to simulate the transferring and transforming of pollutants in unsaturated soil.