Abstract: With the development in the past 25 years, the Global Navigation Satellite System (GNSS) atmospheric radio occultation (RO) has been found to be an effective method to detect the near Earth’s space environment. Even though the quality of the RO products is high, the bias still exists and could be reduce the effectiveness of tbe RO, especially, the ionospheric effect on the atmospheric RO. The GNSS signal is affected by the ionospheric irregularity, including the sporadic E (Es) and the F region irregularity, in terms of the oscillations of the amplitude and the phase. This effect could reduce the quality of the atmospheric RO products. In this study, based on the data of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) RO, the bending angle oscillation, which is defined as the standard deviation of the bias between the observed bending angle and that obtained with the climatology model of the National Center for Atmospheric Research (NCAR), is used for the statistical analysis. The bending angle oscillation in different altitude intervals is studied. It is found that the bending angle oscillation shows significant variations in the latitude, the longitude, and the local time, which is well consistent with the Es and F layer irregularity occurrence features. Besides, the oscillation related to the ionospheric irregularity effect can be observed from 35 km to 80 km in the bending angles. A better understanding of these effects could benefit both the data retrieval and the applications of the RO in the lower atmosphere.