Abstract: To improve the flocculating performance of the epichlorohydrin and polyamine flocculants, 2-methylimidazole was selected as the crosslinking agent to synthesize a novel quaternary ammonium salt cationic flocculant (MZO) using epichlorohydrin and dimethylamine as the main raw materials. The structure and characteristics of the polymer were studied by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The sample performance was tested in the treatment of the Fushun refinery wastewater and compared with other modified flocculants (the crosslinking agents were methenamine (HMTA), diethylenetriamine (DET), triethylenetetramine (TER), ethylenediamine (ED), triethylamine (TE) and diallylamine (DAA) respectively). The effects of flocculant dosage, temperature and mixed usage with polyferric chloride (PFC) on the performance of the flocculant were studied by single factor experiments. The optimum treatment conditions were determined by an orthogonal experiment. The results showed that the cationic degree of the MZO flocculant was 41.1%, which was not the best. However, the turbidity removal rate of MZO flocculant reached 98.2%, which was 1.2%-20.0% higher than the other six modified flocculants. The optimum conditions were that the flocculation temperature was 55 ℃, the dosage of flocculant was 30 mg/L and the mixed ratio of MZO and PFC was 1∶40 (mass), as concluded from the single factor experiment. The optimum treatment conditions were that the temperature was 55 ℃, the dosage of flocculant was 25 mg/L and the mixed ratio of MZO and PFC was 1∶20 (mass) from the points of the production, economic factors and the orthogonal experiment results. The turbidity removal rate of the mixed flocculant was 98.2%.