As an important part of the transformer insulation structure, the angle ring plays an important role in improving the electric field distribution at the end of the winding and increasing the insulation strength. Its stable performance is critical in ensuring the reliability of the insulation system. The electric field at the end of the transformer is complicated and unevenly distributed. Transformer manufacturers try their best to reduce the insulation distance at the end as much as possible without reducing the insulation strength and costs, the angle rings precisely achieves this function. The selection of raw materials, processing technology, production environment and storage measures are all important factors that affect the insulation performance and technical parameters of the angler ring, and become the key to ensuring the safe operation of the transformer. Therefore, the whole process of quality control measures are adopted in the angle ring manufacturing to ensure the product quality.