Delignification has an important role in biomass utilization framework of Empty Fruit Bunch of Palm Oil (EFB). EFB from Sulawesi Island with high lignin reached 45% was a challenge. Innovation for delignification should be delivered to remove lignin but keep holocellulose, cellulose, and hemicellulose. Treated EFB improved accessible the holocellulose for subsequent process like enzymatic process. Delignification would remove or break down lignin to increase the accessibility. Delignification by ozonized NaOH solution conducted at ambient temperature to save energy and low NaOH concentration, 3.2%. Ozonization NaOH solution with 500 ppm H₂O₂ would produce hydroxyl radical (OH°), an oxydator. ORP, TDS, and TSS of black liquor was observed to assess any suspended and dissolved solid of EFB. Treated EFB was analized for its component, lignin, and holocellulose. At higher NaOH solution was the higher TSS in ozonized NaOH solution. The highest TSS by ozonized 0.8 M NaOH reached 50.810 ppm. Unfortunately, the holocellulose was also decomposed as well. Thus, the yield was decrease since both lignin and holocellulose degraded. Optimal delignification was figure out at 0.4 M or 1.6% NaOH whereas lignin decreasing and holocellulose increasing by 30.8% and 27.17%, respectively. XRD analysis clarified improvement of this delignification for crystallinity increased 8.5%, 69%, closer to α-cellulose. Morphology by SEM showed remove the impurities successfully and Si, Nb, Mg, and Ca detected by EDS.