A secondary cell residual capacity calculation method and a battery pack capable of calculating the secondary cell residual capacity is provided. The calculation method includes detecting a temperature of a plurality of secondary cells; detecting a current and a terminal voltage of the plurality of secondary cells; digitizing temperature, current, and terminal voltage; calculating a cell polarization voltage from the digitized temperature, current and terminal voltage; calculating an original cell voltage from both of the calculated cell polarization voltage and the detected terminal voltage; and calculating a residual capacity rate based on the calculated original cell voltage with reference to a prearranged residual capacity reference data table.