Abstract: In order to analyze the relationship between the voltage sag immunity and the parameter configuration of the adjustable speed drive（ASD）,this paper studies the theoretical calculation approaches of voltage sag immunity and the parameter design of ASD.There are two key parameters discussed here.One is the threshold of DC under-voltage protection,the other is the capacitance on DC side.Firstly,the relationship between voltage sag immunity and the two key parameters is analyzed and the mathematical expressions are given to calculate the voltage sag immunity of ASD in the most severe case.Secondly,depending on the demand of voltage sag immunity,the mathematical expressions are given to help the parameter design.Thirdly,the testing platform and simulation model for voltage sag immunity of ASD are developed.Finally,by the comparison of calculation,simulation and testing results,the effectiveness of the proposed approaches has been verified.The proposed approaches can reduce the hard work of the operational test and improve the efficiency of the parameter design,which can be considered as the basis of solution for the compatibility between power suppliers and end-users.