The calibration technology of radar reflectivity is directly related to the precision of radar quantitative measurement, being the fundamental factor for radar observation. Taking CINRAD/CC radar as an example, the principles of automatic calibration technology, the DDS (Direct Digital Synthesis) technique, which is used in calibration, and the implementation procedures are described in detail. The precision of automatic echo intensity calibration was measured and the testing results are given. The findings conclude that CINRAD/CC can ensure the precision less than 1 dB while the transmitter power and receiver gain change. The factors influencing the precision of automatic calibration are also analyzed.