Abstract: An electric curtain mainly utilizes a covering sheet furled at an upper limit position, which simultaneously impels an actuating member of a zero device to relatively cooperate with a sensor of the zero device, so that the covering sheet would not continue operating and a counter in the zero device would recount once a processing unit of a controlling device receives a signal from the sensor. Thus, the processing unit would drive the counter to recount in every following drop of the covering sheet to accurately control the suspending position without incurring an accumulative counting error and increase an operative convenience.