The invention discloses a controlling apparatus for a signal outputting circuit in an electronic system. The controlling apparatus includes a detecting circuit, a switch, and a controlling circuit. The detecting circuit is used for detecting whether the electronic system has an abnormal condition. The switch is electrically connected between a signal receiving terminal and the signal outputting circuit. The controlling circuit is electrically connected between the detecting circuit and the switch. Once the detecting circuit detects that the electronic system has the abnormal condition, the controlling circuit sets the switch into a high-impedance state.