A single pole two-wire system phase control trailing edge light modulating circuit, comprising: a full-bridge rectification circuit, a power supply circuit, a light-modulating control circuit, a voltage detection circuit and an active switch; wherein the full-bridge rectification circuit has one input terminal connected to a live wire and the other input terminal connected to a light-emitting load which is further connected to a neutral wire; the power supply circuit, the voltage detection circuit and the active switch are all connected in parallel between a positive output terminal and a negative output terminal of the full-bridge rectification circuit; three inputs of the light-modulating control circuit are connected to the negative output terminal of the full-bridge rectification circuit, to an output terminal of the power supply circuit, and to an output terminal of the voltage detection circuit, respectively; and an output terminal of the light-modulating control circuit is connected to the input terminal of the active switch, characterized in that the full-bridge rectification circuit is adapted to convert an AC electrical supply into electrical supply of positive half cycle of a sine wave which is used as an input power supply for the power supply circuit, the voltage detection circuit and the active switch; the power supply circuit is adapted to provide a stable DC working voltage to the light modulating control circuit and to the active switch in a linear voltage manner; the light-modulating control circuit comprises a retriggerable dual monostable integrated circuit IC 4528 as the core, the voltage detection circuit is adapted to produce a triggering signal for the light modulating circuit when the voltage of each input half cycle is lower than a preset voltage detection value; upon receiving the trigger signal from the voltage detection circuit, the light modulating control circuit is adapted to generate first and second delayed signals simultaneously, with the first delay control signal controlling the conduction phase angle of the active switch and the second delay signal shielding the trigger signal generated by the voltage detection circuit so as to prevent a secondary trigger in one delay period; and the active switch, utilizing a field effect transistor as a switch, is adapted to switch on/off according to the first delay control signal of the light modulating control circuit to achieve control of a conduction phase angle of the electrical supply to the light-emitting load. a full-bridge rectification circuit, a power supply circuit, a light-modulating control circuit, a voltage detection circuit and an active switch; wherein the full-bridge rectification circuit has one input terminal connected to a live wire and the other input terminal connected to a light-emitting load which is further connected to a neutral wire; the power supply circuit, the voltage detection circuit and the active switch are all connected in parallel between a positive output terminal and a negative output terminal of the full-bridge rectification circuit; three inputs of the light-modulating control circuit are connected to the negative output terminal of the full-bridge rectification circuit, to an output terminal of the power supply circuit, and to an output terminal of the voltage detection circuit, respectively; and an output terminal of the light-modulating control circuit is connected to the input terminal of the active switch, characterized in that the full-bridge rectification circuit is adapted to convert an AC electrical supply into electrical supply of positive half cycle of a sine wave which is used as an input power supply for the power supply circuit, the voltage detection circuit and the active switch; the power supply circuit is adapted to provide a stable DC working voltage to the light modulating control circuit and to the active switch in a linear voltage manner; the light-modulating control circuit comprises a retriggerable dual monostable integrated circuit IC 4528 as the core, the voltage detection circuit is adapted to produce a triggering signal for the light modulating circuit when the voltage of each input half cycle is lower than a preset voltage detection value; upon receiving the trigger signal from the voltage detection circuit, the light modulating control circuit is adapted to generate first and second delayed signals simultaneously, with the first delay control signal controlling the conduction phase angle of the active switch and the second delay signal shielding the trigger signal generated by the voltage detection circuit so as to prevent a secondary trigger in one delay period; and the active switch, utilizing a field effect transistor as a switch, is adapted to switch on/off according to the first delay control signal of the light modulating control circuit to achieve control of a conduction phase angle of the electrical supply to the light-emitting load.