Using the density functional theory and its combination to the dynamical mean field theory (DMFT), we have studied the electronic and magnetic structures of Fe-based superconductors, AFe2As2 (A=Ca, Sr, Ba). Our results for the electronic structure agree well with existing angle resolved photoemission spectroscopy (ARPES) data. The temperature dependent magnetization has been calculated using DMFT, and the magnetic transition temperatures are reasonably consistent with the experimentally observed trend for three compounds.