The emergence of magnetic guided butted well technology has greatly improved the connectivity of docking. Now the technology is widely used in the mining of natural alkali and other minerals. With the continuous development of this technology， as an excellent representative of the underground “thread the needle” navigation tool—SmartMag drilling target-hitting guide system， with its excellent measurement accuracy， stability and reliability， has made hundreds of good achievements in the water solution mining butted wells at home and abroad.From the perspective of science popularization， this paper introduces the necessity of downhole docking navigation， the composition and principle of SmartMag system， the development process of SmartMag system and the achievements made in recent years， so as to improve everyone’s understanding of the SmartMag system， achieve the purpose of mutual exchange and mutual promotion， and finally promote the continuous development of the technology and the continuous expansion of the application field of the active magnetic measurement system represented by SmartMag system.