The invention discloses a method for determining a power battery SOP, which includes steps of step 1, selecting temperature, polarization voltage, duration time, SOC and SOH of a measurement target; step 2, adjusting the battery to the target temperature, SOC and SOH; step 3, adjusting the battery to the target initial polarized voltage; step 4, acquiring discharge coulombic efficiency at set timeunder an appointed rate; step 5, acquiring the charge coulombic efficiency at set duration time under the appointed rate; step 6, performing curve line and curve face function fitting on results acquired in steps 4 and 5; step 7, acquiring battery damage evaluation of given power under a given condition according to the fitting result, and acquiring the maximum bearable power of the battery. Themethod for determining the power battery SOP has the advantages of directly carrying out quantitative evaluation on battery volume loss by coulombic efficiency, providing a reliable basis for the battery power used by the control strategy, setting the initial polarized voltage condition; the method includes the influence of using history on the SOP, thus the measurement is more exact and reliable.