Abstract: Uncertainties in cloud simulations can affect key physical processes in climate simulation. Using satellite data from CloudSat/CALIPSO and CERES and ERA5 reanalysis data, this study analyzes the distribution characteristics of global climatological cloud fraction and cloud radiative effects (CRE) simulated by the atmospheric component FAMIL in the climate system model FGOALS-f3 at resolutions of 100km, 25km, and 12.5km, and discusses the potential sources of simulation errors based on Xu-Randall cloud diagnostic scheme. The results show that at different resolutions, the cloud fraction simulation is underestimated (overestimated) in low (high) latitude areas, and the simulation technique changes nonlinearly with the increase of resolution. On the global scale, the deviation of the 25km model is increases compared with the 100km model, and the cloud fraction deviation of 12.5km model is about 4% higher than that of 25km model in regions like the Western Pacific Warm Pool. After the model resolution increases, the simulation of CRE is lower with the decrease in cloud fraction. In the Xu-Randall scheme, relative humidity (RH) is the dominant factor controlling climatological cloud fraction. Resolution enhancement will further change RH through affecting variables such as temperature and vertical velocity, indirectly affecting cloud deviation. The weak vertical velocity of the 100km model indirectly leads to the underestimation of cloud fraction in the middle and high layer at low latitudes. Compared with the 100km model, the higher temperature of the 25km model increases the cloud fraction deviation. Compared to the 25km model, the temperature of the 12.5km model is lower than that of the 25km model, resulting in a decrease in the cloud fraction deviation.