Dominated by atmospheric temperature,pressure and water vapor pressure,the atmospheric refractivity affects both the propagation path of radar EMwaves and the echo phase of an object.This implies that the variation of atmospheric refractivity can be retrieved by calculating changes of echo phase measured by Doppler weather radar.Thus the relevant water vapor information can be obtained for the research of local convection or advection.This paper explains the principle and method of refractivity retrieved from Doppler weather radar.The experiment results showed that the atmospheric refractivity retrieved from the Sband Doppler radar of Jiangsu Meteorological Observatory was reliable and effective in the case of a local thunder storm.The work can supply not only the remotesensed data to the study on changes of water vapor and weather changes but also supporting data of water vapor field to numerical models,which is very promising in application.