Flange joint is an important component in pipeline connection, which is widely used in petroleum, chemical industry, water supply and drainage, HVAC and other fields. It tightly fixes the two flanges together by bolts to form a sealed connection, ensuring the safety and stability of fluid transmission. The main materials of flange joints include carbon steel, stainless steel and cast iron. Different materials are selected according to the use environment to meet the requirements of pressure resistance, corrosion resistance and high temperature. The structure of flange joints in various forms, common are flat welding flange, welding flange, plate flat welding flange and loose flange, etc. Each type is suitable for different working conditions. For example, flat-welded flanges are suitable for low-pressure environments, while butt-welded flanges are used for high-pressure and high-temperature applications. The design of flange joints should follow relevant standards, such as GB, American ASME or European EN, to ensure product consistency and interchangeability. The advantages of flange joints are easy installation, reliable connection and easy maintenance. However, the disadvantage is that it is heavy, costly, and may cause leakage due to vibration or temperature changes. Therefore, in practical application, the correct selection and strict construction must be made to ensure that the flange butt surface is flat, the sealing gasket is suitable and the bolts are tightened evenly. With the development of industrial technology, flange joints are constantly innovating. The application of new materials and the improvement of manufacturing process have improved the performance of products and reduced the production cost. In addition, flange joints are developing in the direction of lightweight and modularization to meet the needs of modern industry for high efficiency and energy saving. In general, as the core component of the pipeline system, the quality and performance of the flange joint directly affect the operation effect of the whole system, and play an irreplaceable important role.