A bipolar high step-up Cuk-Sepic converters based on the ‘coat circuit’ is proposed, which can be used to connect single photovoltaic (PV) panel and inverters. Like the basic Cuk or Sepic converter, it contains only one active switch, so its control method and drive circuit are simple to achieve. The conversion ratio of the proposed converter is effectively increased through a ‘coat circuit’, and the voltage stress of the devices is reduced. In addition, the positive and negative voltages of the bipolar output voltage of the converter can be automatically equalized. Working principle and performance analysis of the proposed converter has been given in this paper in detail, and a 266.7W experimental prototype using GaN MOSFET has been built to verify the correctness and effectiveness of the theoretical analysis.