Abstract: A trajectory mapping method, called MagCom, is proposed based on the geomagnetic perception of indoor mobile devices. MagCom gets the initial position by means of Wi-Fi localization technology, and then calculates the instantaneous position of users continuously leveraging data of the phone's built-in inertial sensors in real time by the floors plan. The magnetic field data of the pedestrians location are captured to calibrate the mapping trajectory of mobile devices with the least squares algorithm. Furthermore, the unit vector and the norm vector are applied to reduce outliers in the searching algorithm. The experimental results show that the proposed method can not only improve the trajectory mapping accuracy but reduce the computational complexity than the state of arts.