According to the principle of the device and the magnetic field of the drive coil, the motion model of emitter was deduced based on the linear inductance model. A simplified calculation method for the force and the acceleration of emitter in the coil was given and some influence factors were concluded. The force to the different shapes of emitter in the coil was simulated by ANSYS Maxwell. All of these provided the guide for the further design and optimization of emitter used in reluctance launch system.