Abstract: In order to study the sedimentation characteristics and action mechanism of cationic polyacrylamide (CPAM) with different ionic degrees on the high muddied coal slime water, the particle size composition and mineral composition of the high muddied coal slime water from Lijiahao Coal preparation Plant were studied. The influence of ionic degree of CPAM on sedimentation velocity, turbidity of clarification zone, thickness of compression zone and sedimentation kinetics of high muddied coal slime water was studied by using the experimental method of flocculation sedimentation of coal slime water. Zeta potential on the surface of slime particles was measured, and the effect of CPAM with different ionic degree on the zeta potential of slime particles was analyzed. The stability of coal slime water under different ionic conditions was studied by using Turbiscan Lab stability analyzer. Based on the sedimentation characteristics and dynamic stability of coal slime water, the sedimentation mechanism of CPAM ion degree on coal slime water was analyzed. The results show that large amount of kaolinite particles and high content of fine particles are the main reasons for the difficult settlement of coal slime water. Under the same dosage, CPAM has a poor sedimentation effect on coal slime water when the ionic degree is low. When the ionic degree is high, the sedimentation velocity of coal slime water is lower, the thickness of compression zone is higher, and the turbidity is lower. The sedimentation effect of coal slime water is good when the ionic degree is high, and CPAM with ionic degree 30%-60% has the best sedimentation effect when the dosage is 36 g/m³, with fast sedimentation speed, low turbidity and thin compression zone thickness. CPAM has great influence on the sedimentation effect and stability of coal slime water. CPAM can reduce the Zeta potential value on particle surface, promote the formation of flocs in the sedimentation process of slime water, accelerate the sedimentation speed, reduce the stability of slime water and turbidity after the sedimentation of coal slime water, due to its long chain containing positive active groups that can easily adsorb with the surface of negatively charged slime particles. The principle of action with coal slime water is “electric neutralization”, “adsorption bridge” and “net capture and sweep”. It is a kind of excellent coal slime water treatment agent.