The invention provides a spectrum sensing method of an electric power radio-on-fiber system. The electric power radio-on-fiber system comprises a base band unit special for electric power, a far-end unit and a communication terminal. The spectrum sensing method includes the following steps that the far-end unit and the communication terminal conduct independent spectrum sensing to provide basic data for cooperation spectrum sensing; first-level cooperation on the side of the far-end unit is executed; if the first-level cooperation cannot determine whether a target sensing frequency band is idle or not, second-level cooperation on the side of the base band unit is executed. According to the spectrum sensing method of the electric power radio-on-fiber system, the framework features of the electric power radio-on-fiber system and the features of a practical application scene are combined, rough detection and fine detection are combined, and the spectrum sensing method has the advantages of being capable of reducing sensing power consumption, improving the sensing accuracy and shortening the sensing time and the like.