The invention provides a characteristic parameter calculation method and device which are used to solve a problem that power system short circuit current direct current component characteristic parameter calculation has great deviation in the prior art. The characteristic parameter calculation method comprises the following steps of according to short-circuit current waveform data which is changedalong with time on an time axis, defining a first discrete function; defining or differentially defining a second discrete function according to a first discrete function integral, wherein the seconddiscrete function is evaluated in a time domain interval; and substituting the value of a first moment and the value of a second moment into the second discrete function to obtain a characteristic parameter, wherein the characteristic parameter includes a time constant and a direct current component initial value, the first moment is the moment in the time domain interval, and the second moment is the moment different from the first moment in the time domain interval.