Abstract: In this paper, the magnetic flux leakage detection technology is used to study the short-circuit small-diameter tube detection technology. A three-dimensional finite element model of small-diameter tube defect magnetic flux leakage detection is established, and the spatial distribution characteristics of the leakage magnetic field are obtained. By changing the influencing factors such as depth and width of defects, the influence of corrosion defect parameters on the leakage magnetic field signal is studied, and the spatial distribution characteristics of the leakage magnetic field are found. A short-circuit small-diameter tube magnetic flux leakage detecting device was developed, and the inner diameter of the small-diameter tube with a size of φ27 mm×3.5 mm was artificially simulated and the test was performed. The experimental results show that the magnetic flux leakage detection technology can realize the detection of short-circuit small diameter pipes.