<p>Mixed office waste (MOW) paper has become a major source of high-quality recycled fiber feedstock in the paper industry due to its strong fiber properties, high whiteness, and low cost. However, impurities such as ink and adhesives, which are difficult to remove from office paper affect clean production and the high-quality use of MOW recycled fiber. In this study, Ca²⁺, starch, and water-based ink were used to explore the effects of non-fiber components on the enzymatic activity of cellulase. Cellulase deinking treatment was applied to MOW waste paper with varying levels of non-fiber components to weaken their physical barrier effect on enzyme–substrate interaction and obtain a colloidal chemical environment more favorable for enzyme action. The results indicated that reducing non-fiber components enhanced the enzymatic deinking effect. The optimum whiteness of MOW feedstock increased by 3.21% according to the International Organization for Standardization standard, after partial removal of non-fiber components, and ink residue decreased from 42.90 to 25.70&#xa0;mg/kg. This study supports the application of bio-enzymes in MOW deinking for the paper industry.</p> Graphical abstract <p></p>