The invention discloses a quantum key distribution system and a control method suitable for a complex channel environment; the system comprises a quantum key distribution system sending end and a quantum key distribution system receiving end, which are arranged at the two ends of an overhead optical fiber; the quantum key distribution system sending end comprises a QKD transmitting end, a polarization feedback signal transmitting end and a time division multiplexing device; the quantum key distribution system receiving end comprises a QKD receiving end and a polarization feedback signal receiving end; the QKD transmitting end and the transmitting end of the polarization feedback signal transmitting end are respectively connected with the receiving end of the time division multiplexing device; the transmitting end of the time division multiplexing device is connected with the polarization feedback signal receiving end through an optical fiber channel; and the transmitting end of the polarization feedback signal receiving end is connected with the receiving end of the QKD receiving end. The time division multiplexing device is additionally arranged in the quantum key distribution system sending end; signal light and reference light are transmitted through a time division multiplexing mode when polarization feedback is needed, so that mutual interference between the reference light and the signal light can be prevented.