Abstract: On the grounds of main technical data of the imported three-high, 24-stand stretch pipe reducing mill located at the facility of Hengyang Steel Tube Co., Ltd., the paper introduces features and speed regulating method of the tandem centralized differential transmission system.In addition, comparision between the said tandem centralized differential transmission system, the centralized differential transmission system and the individually electric speed-regulating transmission system are made in terms of advantages and disadvantages.