Abstract: Electrical conductivity and water hardness are important indicators of water quality of coal slurry system.The tests was done to study the Changes of water quality between the one-time single-point and single point continuously of adding the flocculants in the test points of the slime slurry system,and hardness and conductivity of the water quality were compared.Test results show that there is a law of change of water hardness and conductivity in slime water system,and the change is obvious impacted by the way of the addition method of flocculants.