Abstract: A recently developed stochastic subgrid cloud generator (SCG) and inde pendent column approximation (ICA) are used to study the effect of horizontal he terogeneity and vertical overlap of clouds on global radiative fields. Results of experiments IHCLD (Inhomogeneous Clouds) and HCLD (Homogeneous Clouds) show that horizontally inhomogeneous clouds lead to both larger net shortwave flux at s urface (FSNS) and larger net longwave flux at the top of atmosphere (FLNT). The largest (about 1 W/ m2 ) and second largest (about 0.6 W/ m2) increases in FSN S occur at the higher latitude where low clouds dominant and in the tropics wher e convection movement is quite active, respectively. However, the largest increa ses in FLNT (about 0.3 W/ m2) occur in the tropics due to tremendous high cloud s. Experiments GenO (General Overlap) and MRO (MaximumRandom Overlap) suggest a stronger signal of impact on the shortwave and longwave radiation budget. Regi onally, the most significant differences of FSNS reach up to 30- 40 W/ m2 in ITCZ regions, as well as a zonal mean difference of about 5 W/ m2 at the highe r latitudes with large amount of low clouds. There are similar spatial distribut ions for the differences of FLNT, but with smaller value. Overlapassumption sh ift can also trigger opposite changes to radiative heating rate in the upper and lower atmospheric layers, thus influences the thermodynamic structure of the at mosphere. The impacts of cloud horizontal and vertical structure on radiation bu dget will surely carry over to the thermodynamic, dynamic status and water vapor conditions of the atmosphere, and consequently change the evolution of modeled climate. The offline cloudradiation calculation makes the results generally applicable, so as to provide valuable information when parameterize cloudradia tion process in different models.