Abstract: The characteristics of atmospheric attenuation in microwave band (λ=5 mm-3.2 cm) are studied.Experimental results from the measurements of atmospheric attenuation by using solar radiation method and atmospheric radiation method in Beijing are compared with values calculated from radiosonde data to analyze their dorrelativity. The relationship between the atmospheric microwave absorption and total water vapor content or surface meteorological factors (for example, temperature, specific humidity) are discussed. It reveals the possibility o,I prediction of atmospheric microwave absorption. Effects of cloud on attenualion are also described.