An approach based on the correlation between two intensity distribution images of the object wave is proposed to determine the phase-shifting value in two-step phase-shifting digital holography. By changing the phase-shifting values used for reconstruction in a certain range around the nominal phase-shifting value,a series of correlation coefficients between the object intensity recorded by CCD and the same intensity reconstructed by computer are obtained. The accurate phase-shifting value will be determined when the correlation coefficient reaches its maximum. The real phase-shifting value is successfully extracted in computer simulations by this method,thereafter the approach is employed in LED-based digital holography. The quality of the reconstructed field by using the obtained value and the nominal value are compared. The feasibility of this method has been verified by both computer simulations and experiments.