As a steel pipe product with a special structure, internal threaded steel pipe has an irreplaceable and important position in industrial heat exchange, petrochemical equipment, air conditioning systems and energy engineering. Its inner wall is made into a spiral or corrugated thread structure through mechanical processing or forming process. This design greatly increases the effective contact area of the inner wall of the pipe, and has significant advantages in enhancing heat transfer, disturbing fluid, improving mass transfer and improving system efficiency. With the development of industrial technology, the performance requirements for internal threaded steel pipes are increasing, and the selection of its specification parameters has become more and more critical. Understanding and mastering its detailed specifications is of great significance to ensure stable, safe and efficient operation of equipment.