Abstract: Gain compression is an item that should be measured specified in the calibration specification and verification regulation for spectrum analyzers. However, the calibration method and the verification method for measuring gain compression are not perfect. The definition of gain compression, common methods of measuring gain compression, and the shortcomings in the calibration method and the verification method are analyzed in this paper. An improved two-tone compression method for measuring gain compression is proposed. It was verified that the new method can measure the 1 dB gain compression point of spectrum analyzers correctly. The method can be used as a supplement to the exiting calibration method and verification method.