ETT-3.7 anode saturable reactor is an LTT reactor developed by Jiashan Huarui SUN.KING Company for Siemens converter valves. LTT reactors have been in operation for more than 30 years. During operation, the reactors have encountered problems such as iron core fragmentation, loud noise, water channel blockage, and water leakage. According to the structural characteristics of the LTT reactor, the R&D team of SUN.KING Company finally determined the design structure of the reactor. The final product structure is a shell-type symmetrical connection structure with two left and right units. The newly designed reactor adopts a single-branch water channel structure to avoid the risk of water leakage caused by too many water channel joints in the reactor; the reactor adopts an elastomer packaging structure to avoid the loosening and fragmentation of the reactor core, and effectively reduces the noise of the reactor. The final designed reactor meets all the requirements of the converter valve in terms of electrical performance. The newly designed reactor can realize the ready-to-use of the LTT reactor in terms of installation size, electrical connection, and water channel connection. In April 2021, the ETT-3.7 reactor produced by our company has been successfully used in the converter valve of the Fulong renovation project.