Abstract: Spectrum sensing is the core of cognitive radio, dynamic spectrum distribution and electronic reconnaissance. Universal experiment of spectrum sensing can be used in many relevant courses. Spectrum sensing experiment can be reconstructed by programming and be applicable to wide frequency range and signal diversity. This paper introduces the software platform with USRP and GNU Radio first. Then basic theory of spectrum sensing is discussed. We design experiments based on energy detection. Finally, frequency modulation broadcasting in city is chosen as an example to show the procedure and results of spectrum sensing.