The invention is applicable to the field of digital television terminals and provides a digital television terminal and a method and a device for controlling the on and off of a power supply of external equipment thereof. The method comprises the following steps: when the digital television terminal starts up, controlling a commercial power loop out to be turned on to provide a power supply for the external equipment of the digital television terminal; when the digital television terminal receives a standby signal, querying if a user needs to turn off the power supply of the external equipment; and when the user needs to turn off the power supply of the external equipment, turning off the commercial power loop out of the digital television terminal by the digital television terminal. In the invention, a main board processes the standby signal or a standby ending signal to generate a commercial power loop out control signal, a power supply board controls the on and off of the power supply of the external equipment of the digital television terminal according to the commercial power loop out control signal and the user can synchronously turn on and off digital television terminal and the external equipment of the digital television terminal by controlling the power supply of the digital television terminal, so the realization is simple, the operation is convenient and the unnecessary energy consumption is reduced.