The invention discloses a shunt impedance parameter determining method for measuring a transient current, and solves a problem that a conventional miniature impedance determining method cannot accurately measure a shunt impedance parameter because of low measurement precision. The method employs a variable frequency AC current source, a multi-purpose meter, a lock-in amplifier, a reference impedance element, and an RLC analyzer which is used for measuring an impedance angle of the reference impedance element. The reference impedance element should meet requirements that a relative error can be neglected when the RLC analyzer is used for measuring an impedance value and the impedance angle can be obtained accurately. The method provided by the invention provides a solution to a problem that a conventional RLC analyzer or network analyzer cannot precisely determine an impedance parameter of a shunt because the impedance parameter of the shunt is too small. The method can precisely determine the shunt impedance parameters at different frequency points according to a frequency component of the transient current, is good in determining results of the shunt impedance parameters, and is accurate and reliable.