High resolution angle-resolved photoemission spectroscopy (ARPES) measurements are carried out on CaKFe4As4,KCa2Fe4As4F2 and (Ba0.6K0.4)Fe2As2 superconductors.Clear evidence of band folding between the Brillouin zone center and corners with a (π,π) wave vector has been found from the measured Fermi surface and band structures in all the three kinds of superconductors.A dominant √2 × √2 surface reconstruction is observed on the cleaved surface of CaKFe4As4 by scanning tunneling microscopy (STM) measurements.We propose that the commonly observed √2 × √2 reconstruction in the FeAs-based superconductors provides a general scenario to understand the origin of the (π,π) band folding.Our observations provide new insights in understanding the electronic structure and superconductivity mechanism in iron-based superconductors.