Abstract: With the rapid development of the coal industry, the problem of slime water treatment is increasingly serious. Slime water contains a large number of fine coal particles and impurities. Conventional treatment methods often have problems such as low treatment efficiency, waste of resources and secondary pollution. Therefore, the development of efficient and green flocculant has a very important application prospect in coal slime water treatment. In this study, a new cationic flocculant CS-g-ADM was synthesized by microwave heating method with chitosan (CS) as the main chain, acrylamide (AM) and d diallyl dimethyl ammonium chloride (DMDAAC) as the graft side chain, under the optimal conditions of 35% total monomer concentration, 1∶1 monomer mass ratio, 60 ℃ temperature and 4% initiator mass fraction. The structural characteristics of the flocculant were studied by FT-IR, XRD, TG and SEM. It was found that the functional groups of AM and DMDAAC were successfully grafted onto the CS main chain. The new molecular weight of the flocculant was 1000, the cationic degree was 32, and it had a typical porous sponge structure and good thermal stability. CS-g-ADM has good flocculation, sedimentation and dehydration effect on coal slurry water. When the optimal dosage of CS-g-ADM is 6 mg/L, the sedimentation rate of coal slurry water is 63 cm/min, the light transmittance of supernatant is 93%, and the water content of vacuum suction filter cake is 21.95%. Zeta potential analysis shows that bridging and electric neutralization are the main flocculation mechanisms. FBRM test shows that after adding CS-g-ADM, the number of fine particles in coal slurry water is significantly reduced, while the aggregation of large particles is increased, which further verifies the flocculation effect of flocculant. These two effects jointly promote the aggregation of particles. The comparison effect is better than that of commercial cationic polyacrylamide (CPAM) and anionic polyacrylamide (APAM), and its green environmental performance is also better than that of traditional flocculants, which has a wide application prospect.