Chapter 3 focuses on the preparation and quality control of inorganic polymer coagulants. Firstly, polyaluminium chloride is introduced, covering its form distribution in solution, including the form of Al(III), the environmental effects of polyaluminium, etc. It also involves the synthesis method of polyaluminium chloride, related resource utilization and chlorination production, as well as drying methods and main properties. At the same time, the preparation method of polyaluminium chloride (PPAC) is described. There is also the impact of the implementation of the new standards on the industry. Then, polymeric aluminium sulfate was expounded and its synthesis method was explained. Then, for polymeric ferric sulfate, its properties and synthesis methods are introduced. Then, we will explain polyferric chloride, covering its synthesis principle and process. Finally, the relevant content about polymeric ferric chloride sulfate and polymeric ferric aluminum sulfate is mentioned.