A decorative LED light string structure, comprising: a plurality of LED light-emitting units, each of the LED light-emitting units comprising an RGB light-emitting diode and a control IC, the RGB light-emitting diode having a common pin and three electrode pins, the control IC capable of storing an address code of the control IC, the control IC having a positive power terminal, a negative power terminal, and three control terminals capable of controlling illumination of a corresponding RGB light-emitting diode; wherein in each of the LED light-emitting units, the common pin of the RGB light-emitting diode is connected to the positive power terminal or the negative power terminal of a corresponding control IC, the three electrode pins of the RGB light-emitting diode are respectively connected to the three control terminals of the corresponding control IC, and wherein a light string is formed by connecting the LED light-emitting units in series or in parallel, characterized in that, the RGB light-emitting diode is capable of generating a periodical micro current according to a corresponding inputted optical encoding signal formed by illumination of different frequencies, the generated micro current flowing through a first resistor to generate a voltage signal; the control IC also has a write terminal capable of writing the address code of the control IC; each of the LED light-emitting units also comprises a voltage amplifier circuit, and the voltage amplifier circuit has an input terminal and an output terminal; in each of the LED light-emitting units, the input terminal of the voltage amplifier circuit is connected to one of the electrode pins of a corresponding RGB light-emitting diode to amplify the voltage signal from the RGB light-emitting diode, and the output terminal of the voltage amplifier circuit is connected to the write terminal of the corresponding control IC to input an amplified voltage signal into the control IC; and the control IC is configured to generate a corresponding address code of the control IC according to a period of the voltage signal. a plurality of LED light-emitting units, each of the LED light-emitting units comprising an RGB light-emitting diode and a control IC, the RGB light-emitting diode having a common pin and three electrode pins, the control IC capable of storing an address code of the control IC, the control IC having a positive power terminal, a negative power terminal, and three control terminals capable of controlling illumination of a corresponding RGB light-emitting diode; wherein in each of the LED light-emitting units, the common pin of the RGB light-emitting diode is connected to the positive power terminal or the negative power terminal of a corresponding control IC, the three electrode pins of the RGB light-emitting diode are respectively connected to the three control terminals of the corresponding control IC, and wherein a light string is formed by connecting the LED light-emitting units in series or in parallel, characterized in that, the RGB light-emitting diode is capable of generating a periodical micro current according to a corresponding inputted optical encoding signal formed by illumination of different frequencies, the generated micro current flowing through a first resistor to generate a voltage signal; the control IC also has a write terminal capable of writing the address code of the control IC; each of the LED light-emitting units also comprises a voltage amplifier circuit, and the voltage amplifier circuit has an input terminal and an output terminal; in each of the LED light-emitting units, the input terminal of the voltage amplifier circuit is connected to one of the electrode pins of a corresponding RGB light-emitting diode to amplify the voltage signal from the RGB light-emitting diode, and the output terminal of the voltage amplifier circuit is connected to the write terminal of the corresponding control IC to input an amplified voltage signal into the control IC; and the control IC is configured to generate a corresponding address code of the control IC according to a period of the voltage signal.