Abstract: Permeability coefficient is an important engineering design precipitation of hydro--geological parameters, Due to the complexity of the hydrogeological and their diversity, resulting in the calculation of permeability coefficient values often lead to big differences. In this paper,Xi'an Metro Line't train station pumping test, the related using complete steady stream of well single well method with observation wells mathematical model, also considering the single--well well the complete loss of mathematical model of steady flow non- complete mathematical model of steady flow wells, water level recovery method mathematical model of an integrated three methods to determine the permeability of loess. Analyzing and comparing the advantages and disadvantages of various mathematical models, equations for calculating the permeability coefficient of loess more reasonable mathematical model.