This study investigates whether a froth flotation-ozone treatment(FFOT) after a alkali soaking treatment is necessary for strength improvement of KOCC. FFOT after a caustic soaking treatment presents optimum process for strength improvement of KOCC. It shows that the components and strength of KOCC behave differently during FFOT after sodium hydroxide treatment. Using optimum conditions, the KOCC compression index increase 30% with pulp consistency and 40% with number of alkali soaking treatment whereas the KOCC ash content decreases 20% above, during FFOT. Also the KOCC holocellulose increases but the KOCC lignin and residue starch content show a clear decrease tendency during FFOT.