The utility model discloses a driving circuit of a floating switch tube. The utility model discloses a power optimizer and a photovoltaic system. the control end of the switch tube is connected with adriving power supply; The driving circuit comprises: a driving circuit, Voltage stabilization module, wherein the switch tube is arranged between a control end and a floating end of the switch tube;and the voltage stabilizing circuit is used for stabilizing the voltage between the control end and the floating end at the driving voltage of the switch tube. at the moment, the control end of the switch tube and the floating end are not normal driving voltage; The two ends of the control end and the floating end are connected with the voltage stabilizing modules in parallel, the voltage betweenthe control end and the floating end can be stabilized at the driving voltage of the switch tube, it can be guaranteed that the control unit of the switch tube and the voltage of the floating end provide the driving voltage for a driving power source, and driving of the switch tube in the floating state is achieved. And meanwhile, only one driving power supply is adopted to drive a plurality of switching tubes, and an isolation type transformer is not needed, so that a circuit with a plurality of switching tubes can be miniaturized.