An　algorithm　is　proposed　for　extraction　of　the　unknown　phase　shift　steps　and　correction　of　the　phase　shift　error　in　partially　coherent　illuminated　phase-shifting　digital　holography.　The　mean　contrast　of　noise　(MCN)　of　the　reconstructed　amplitude　image　is　developed　to　evaluate　the　noise　level　resulting　from　phase　shift　error.　Actual　phase　shift　steps　are　first　extracted　by　minimizing　the　MCN.　Then　the　extracted　actual　phase　shift　steps　are　used　to　retrieve　the　original　object　wave　without　phase　shift　error.　The　validity　of　the　proposed　method　is　verified　by　simulations,　and　then　implemented　in　partially　coherent　illuminated　phase-shifting　digital　holography　where　a　spatial　light　modulator　with　unknown　phase　modulation　characteristic　is　used　as　the　phase　shifter.　The　results　demonstrated　that　the　actual　phase　shift　steps　can　be　extracted　and　the　phase　shift　error　is　corrected　effectively.　(C)　2015　Optical　Society　of　America