Three water-soluble quaternized cellulose derivatives (QCs) with degree Of Substitution (DS) Values of 0.38, 0.50, and 0.74 were synthesized in NaOH/urea aqueous solutions. The flocculation characteristics of QCs have been evaluated in montmorillonite (MMT) Suspensions and simulated dye (Reactive Red) aqueous Solutions by spectrophotometry. The results showed that QCs were effective flocculating agents for MMT over a wide range of pH values, and then flocculation efficiency of MMT Was Up to nearly 100%. Decolorization efficiency of Reactive Red dye reached 93% Under optimum conditions. In vitro antimicrobial activity of QC was evaluated by determining minimum inhibition concentration (MIC) Values against Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli), respectively. The results showed that QC Could strongly inhibit the growth of E. coli and S. aureus. Therefore, quaternized cellulose is applicable as a novel wastewater treatment agent with high flocculation efficiency as well as effective antimicrobial activity.