Abstract: To study the effects of the stratification changes of water vapor on fog and haze, the variation of visibility relative to the liquid water content and relative humidity observed by microwave radiometer during fog and haze events from October 2011 to February 2012 in Beijing was analyzed. The sequence diagram results showed that atmospheric liquid water content is not a suitable reference for forecasting fog and haze, nor is time variation for forecasting its generation or dissipation. However, the various times in the profile diagram of atmospheric liquid water content can indicate the presence of fog and haze because the stratification of liquid water content obviously changes during the generation and dissipation of fog and haze. Further analysis on the various conditions of the fog and haze showed that variations in relative humidity and liquid water content were concentrated mainly below 3 km. Non-precipitation occurred during fog and haze; fog occurred prior to precipitation, and haze dissipated after the precipitation ended. Under the conditions of heavy fog after precipitation, the variation of atmospheric relative humidity was obvious, and the changing of liquid water content occurred between 3-7 km. Precipitation is favorable for the dissipation of fog because it can increase the humidity level near the ground and consume the water vapor in the air. Heavy fog combined with precipitation resulted in a saturated layer with relative humidity close to 100%, whereas heavy haze with no precipitation did not form a saturated layer, and the relative humidity was relatively low.