Aiming at the low cost and high precision requirements of permanent magnet linear motor rotor position detection, a method based on saddleshaped magnetic field and the process to obtain position were presented. The magnetic field distribution characteristics of the permanent magnet surface were analyzed. The advantages of using the saddleshaped magnetic field distribution curve to obtain the position information were pointed out. The algorithm flow of estimating the position information based on the saddleshaped magnetic field waveform was proposed. First, two saddle curve data of the staggered phase were measured and the database was divided into four quadrants. Second, in the position detection, the interval search algorithm was used to find the best two sets of magnetic field intervals. Finally, according to the accuracy requirements, the appropriate interpolation algorithm was used to calculate the electrical angle. The simulation results showed that the position calculation based on the saddleshaped magnetic field could better meet the requirements of linear motor rotor position detection.