Abstract: In this paper, theoretical deduction, electromagnetic simulation analysis and field test were carried out on the factors affecting the magnetic field transmitter used for pig tracking and positioning in order to improve its transmitting distance. It is shown that the transmitting distance of the transmitter can be improved by installing the transmitter outside the pig steel frame or increasing the coil diameter to reduce the number of the turns of the transmitting coil (copper content of the coil unchanged). When the pigging operation is conducted in a thinner wall pipeline, the transmitting distance can be also increased, but the increment is not obvious. The effect of pipe diameter on transmitting distance is not obvious and can be neglected. The research results are conducive to maximize the transmitting distance of the transmitter and provide the theoretical basis for increasing the monitoring range of the pig.