The atmospheric temperature and specific humidity profiles from 4-yr COSMIC radio occultation (RO) measurements during boreal winter (Nov.-Apr. in 2006-2010) were employed to study the large-scale vertical structure of Madden-Julian Oscillation (MJO). The results indicate that, the temperature anomaly exhibits a trimodal vertical structure moving eastward with MJO convection over the Indo-Pacific region, and the moisture anomaly shows a westward tilt with height over the Indo-Pacific and an eastward tilt over the central and eastern Pacific. Some salient properties of MJO structure are also presented in RO bending angle and refractivity anomalies, for instance: the close relationship between MJO anomalies and tropical convection, westward-tilting structure over active regions of deep convective, and significant MJO anomalies over inactive regions. These MJO features agree well with those revealed using global reanalysis data and meteorological satellite observations, such as the Atmospheric Infrared Sounder (AIRS). Major differences between RO and other datasets are found in temperature MJO anomalies over the tropopause region, where RO data have the best accuracy. The intraseasonal variation of cold-point tropopause is further investigated. The results show that the enhanced convection is preceded by cooling the tropopause and is followed by lowering the tropopause. The MJO structures during two boreal winters, Nov. 2007 – Apr. 2008 (La Niña) and Nov. 2009 – Apr. 2010 (El Niño), are individually presented to explore the ENSO effect on the MJO structure. It is shown that the modification of strength and location of deep convection associated with ENSO modulates the large-scale MJO anomalies accordingly. Significant differences between them are also found over the western Hemisphere.