Because paper industry spends lots amount of water, the reuse from recycling of water is very important in economically as well as environmental aspects. Save all system, like CDS and settling tank, plays an important role in the recycling of water. In this study, the sedimentation efficiency of white water was tested under the different amount of alum addition in order to find the optimum conditions of waste water treatment. At the conditions of alum 100 ppm and A-polymer 1 ppm, the coagulation efficiency was highest and SS density was obtained below 50 ppm from 3 kinds of paper production lines.