Abstract: An electrically operated screw-type jack comprising a support base, a housing, a jack body, a lifting ram being contained in the jack body, a servo motor being contained in the housing, reduction gears for transmitting the driving power of the servo motor to the lifting ram, a safety device for preveting the servo motor and the power transmitting mechanism including the reduction gears from an abrupt failure in overloading the jack, and a square head pin for hand operation of the jack when there is an overload on the jack. The reduction gears consist of first sun and planet gears, second sun and planet gears and a sun gear cylinder. The safety device consists of a clutch disk, a clutch spring and a sleeve. The present invention can provide an electrically operated screw-type jack which can promote the driving power of the servo motor, and prevent its power elements from an abrupt failure when there is an overload thereon.