Abstract: A COMBO ONU optical module circuit is provided, including a MCU control circuit, a XGSPON ONU circuit, and a GPON ONU circuit. The MCU control circuit includes three control units. The first control unit is configured to determine a transmission channel according to a signal level. The second control unit is configured to switch between a TX_SD_10G signal and a TX_SD_1G signal. The third control unit is configured to supply power to the GPONG ONU circuit using PWR_1G control or the XGSPONG ONU circuit using PWR_10G control. The first control unit is further configured to control the XGSPON ONU circuit and the GPON ONU circuit in an I2C communication mode. Under control of the first control unit, the XGSPON ONU circuit is configured to receive and emit a 10G optical signal, and the GPON ONU circuit is configured to receive and emit a 2.5G optical signal.