Abstract: A magnetic speed controlling twist grip assembly includes a linear IC, first and second magnets, a stationary member; and a rotary handle turnably connected to the stationary member at an inward end. The linear IC is disposed in the stationary member. The first and second magnets are disposed at the inward end of the handle such that different magnetic poles thereof face respective ones of opposite sides of the linear IC. The magnetic field around the linear IC is changed when position of the magnets relative to the linear IC is adjusted with the user's hand turning the rotary handle, and in turn, electric currents passing through the linear IC is changed. A control device, to which the linear IC is electrically connected, will control electric power supplied from a storage battery to a motor accordingly, thus controlling speed of the motor.