Abstract: The dual-satellite observations of FY-4A and FY-4B exhibit continuity and complementarity, but differences in the satellites" positions and observation paths may result in inconsistencies in their actual detection results. This study, based on AGRI full-disk Level 1 data and cloud top height products(CTH) from dual-satellite imagers during June-August 2022, conducted parallax correction on the dual-satellite data and analyzed differences in thermal infrared channel brightness temperatures (BT) under various cloud height scenarios and underlying surface conditions. The results show that within the common observation area, the BT differences between FY-4A and FY-4B gradually turn positive to negative from west to east. In the equatorial region, the BT differences can reach 8 K. As cloud height increases, the Root Mean Square Error (RMSE) of the BT differences rises from 1.63 K to 3.06 K. The differences are larger over land than over the ocean. Additionally, this study investigates the theoretical impacts of satellite zenith angle on dual-satellite BT differences using the RTTOV fast radiative transfer model. The simulated BT difference trends between the satellites show broad consistency with observed empirical trends. Therefore, future research could perform physical correction on the dual-satellite observations according to these patterns, enabling joint applications of the dual-satellite data.