In current research, the flocculation performance of cationic polyacrylamide flocculant PAMC with high cationic degree was investigated in HA synthetic water treatment, and the effect of kaolin particles was studied in kaolin-HA flocculation. Influencing factors, such as pH, PAMC dosage, initial HA concentration, cationic degree, stirring speed and stirring time, were investigated and optimized for HA removal efficiency. Two-dimensional fractal dimension of the flocs was analyzed based on flocs images, and FTIR analysis was accomplished to understand chemical structures of the flocs. Three-dimensional excitation emission matrix spectra was measured to analyze the changes in organic composition and concentraion. Finally, the HA and kaolin-HA synthetic water flocculation mechanism were studied and summarized based on analysis of zeta potential and pH. The results showed that 80.7% and 91.2% of HA removal efficiency was achieved in HA and kaolin-HA flocculation process by using 12.5 mg/L and 4-6 mg/L of PAMC, respectively. Moreover, partial colloidal HA was absorbed by kaolin particles before flocculation and was removed in flocculation through synergetic effect from kaolin particles. Charge neutralization and bridging effect was confirmed to be dominant in acidic and alkaline environment, respectively. (C) 2017 Elsevier B.V. All rights reserved.