Zheng Qi Wen Zhang Sheng Hu Gao Yihai Yu Qi Yu Ming Feng Nucl. Electron. Detect. Technol. 524-526 22 6 2002 2002 The author introduces the principle, method and results of RF voltage amplitude measurement by using X-ray energy spectrum. X-ray spectrum measurement method is one well-known method of absolute voltage measurement. It is based on the measurement of X-ray spectrum generated by field emitted (FE) electrons in RF cavity. The voltage amplitude of RF cavity measured by X-ray spectrum method is accurate and reliable. The DEE voltage of HIRFL-SSC cyclotron has been calibrated by X-ray spectrum measurement results