Abstract: In order to obtain the running position of the pipeline internal detector in oil and gas pipeline, low-frequency tracking and positioning system is used for real-time monitoring of pipeline detectors Based on the electromagnetic duality principle, the working mechanism of the launch coil in low-frequency tracking and positioning system was studied using the dipole model. It is shown that the launch coil of low-frequency tracking and positioning system in the near field does not radiate energy outside and the transmitter and the receiver are connected by the magnetic field generated by the launch coil. Then, the distribution characteristics of the magnetic field of the launch coil were simulated using the simulation software ANSYS Maxwell. It is indicated that the axial and radial distribution of magnetic field generated by the launch coil is symmetrical. The experimental results show that the characteristics of the output signal of the receiving coil agree with the simulation results of the magnetic field of the launch coil very well. And besides, the positioning accuracy of low-frequency tracking and positioning system based on the magnetic field distribution characteristics of low-frequency launch coil is ±5 cm, meeting the actual engineering requirements.