Anthropogenic aerosol effective radiative forcing (ERF_aer) is an important metric to quantify aerosol effects on climate in Earth system models. Department of Energy’s Energy Exascale Earth System Model (E3SM) tends to overestimate ERF_aer. Here we analyze ERF_aer simulated in one of the E3SM developmental branches for version 3 candidate that includes a newly implemented predicted particle property (P3) stratiform cloud microphysics scheme and a ZM convective cloud microphysics scheme (ZM-Micro). The results show that the total ERF_aer and its direct and indirect forcing components in this version with the P3 and ZM-Micro are relatively large when compared to the standard E3SM version 2 and other Earth system models. This is, mainly due to the improvements in number concentration and size of cloud hydrometeors in convective clouds by ZM_micro, which result in a large increase in the indirect forcing. Another reason is that the model simulates a much larger aerosol mass burden and a longer aerosol lifetime and thus overestimates aerosol optical depth (AOD), indicating an insufficient aerosol wet removal. By improving aerosol wet removal treatments for deep convective clouds (e.g., cloud-borne aerosol detrainment, aerosol secondary activation, and cloud-borne aerosol removal), we effectively decrease the aerosol burden and lifetime and reduce the positive biases in AOD and aerosol mass concentration. The resultant direct and indirect forcing components of ERF_aer also significantly decrease. On the other hand, the decrease of total ERF_aer magnitude is not drastic, because the weaker (less negative) indirect forcing is offset by the less positive direct forcing. The aerosol overestimation still exists, and more effort is needed to reduce the aerosol overestimation for improving ERF_aer in E3SM.