In recent years, smart phones become increasingly popular. More than having strong computing ability, smart phones are equipped with a variety of sensors. Users can get even more information by the sensors. Among the sensors, magnetic sensor has become the standard equipment on smart phones. In this thesis, we analyze the rotational angle of magnetic sensor on smart phones and calculate the angular velocity and angular acceleration of the smart phones to achieve the capability which is similar to gyro sensor. The magnetic sensor is used to detect the change of the angle and to predict the displacement of the phones moving along the same axis. Finally, the rotational angle, the angular velocity, the angular acceleration of the smart phones and the LMA theory are integrated to determine and classify the users’ motion. Through this determination and classification, the characteristics of user’s motion can be found out.