The specific humidity profiles derived from the GPS（global positioning system） RO (radio occultation) of the COSMIC (constellation observing system for meteorology, ionosphere, and climate) with those from low latitude（30°S~30°N）radiosonde and MACC(monitoring atmospheric composition and climate) reanalysis during the NH (north hemisphere) winters (December, January, and February ) from 2006 to 2012 over the layers from 1000 hPa to 200 hPa were verified. Comparison results demonstrate that the impact of water vapor on the COSMIC GPS RO inversion is very large, especially over the tropical and low troposphere. And the COSMIC GPS RO observations below 850 hpa may not be suitable for the assessment of other observations. 