In water treatment process, one of primary chemicals used is aluminum sulfate as a coagulant forming so the water becomes clean. Aluminum sulfate [Al2(SO4)3] or better known as alum is one of the chemicals that are required both in industry and in water treatment company. This research is purposes to study the operating conditions of the process of making aluminum sulfate liquid of kaolin and sulfuric acid to see the effect of temperature, time, ratio of sulfuric acid and kaolin, the concentration of sulfuric acid, the stirrer rotation and speed on the quality of liquid aluminum sulfate to be generated in order to obtain optimum operating variables conversion process to obtain optimal value. In this research, the process of mixing the sulfuric acid and kaolin, aluminum sulfate paste subsequently extracted with distilled water that has been heated to obtain aluminum sulfate. Fixed variable in this study are the weight and size of the kaolin particles each 25 grams and 250 μ, the condition of the extraction process at a temperature of 100 ° C, the ratio of sediment and hot water 3: 1, while stirring for 1 hour at 3 times the amount of leaching and bone dry conditions. While changing the controlled variable is the time of surgery for 20, 50, 90 and 110 minutes, the ratio of sulfuric acid and kaolin 1: 2; 2: 2; 3: 1 and a sulfuric acid concentration of 30%; 50%; and 70%. The results obtained were the composition of kaolin Jaboi in a preliminary test using x-ray beam, results were obtained that the highest composition is SiO2 as much as 96.9% whereas only 1.26% alumina. Judging from the influence of sulfuric acid concentration on reaction time obtained a yield of 92,13% at 50% concentration sulfuric acid at reaction time 110 minutes.