The invention discloses an improved inrush current identification method. The method includes a main variable data window identification algorithm and an auxiliary acceleration identification algorithm. The method particularly includes: setting threshold values +/-epsilon above and below a time axis respectively, and utilizing the threshold values and an extreme value of a certain section of sampling current to determine a starting point and a finishing point of a variable data window; simulating a standard sine curve forwards and backwards by the extreme value in the selected variable data window according to a sampling interval and data window length, and comparing normalized area indicators of difference area between the standard sine curve and the sampling current so as to realize locking and starting of protection. By the improved inrush current identification method, inrush current waveform and failure current waveform can be differentiated to greatest extent, and when a transformer generates inrush current, locking differential protection can be realized quickly and reliably; mistaken locking differential protection is avoided during inside failure; differential protection can be started quickly when the transformer is switched on in a failure when being no-load; the improved inrush current identification method has high transformer saturation resistance.