An electric window covering has a covering material, a driving device, a microcontroller, a position detecting module and a trigger detecting module. The position detecting module detects a position of a lower end of the covering material to generate a position information. The microcontroller compares the position information with a reference position to generate a position relationship with respect to the reference position. The trigger detecting module detects whether the covering material is moved by an external force for generating a detecting result. When the microcontroller determines that a trigger event is received according to the detecting result, the microcontroller configures the driving device to move the covering material according to the position relationship and the trigger event.