In the process of flocculation and sedimentation of slime water, there are many influencing factors. This paper mainly studies the influence of GT value on flocculation and sedimentation effect under different concentrations of slime water. The results show that the dosage of coal slurry is different when the concentration of coal slurry is different. For a certain concentration of slime water, with the change of GT value, the flocculation and sedimentation effect also shows obvious difference. GT value should not be too high, otherwise the formation process of floc will be destroyed. For this test object, the best GT value should be around 3700.