In this work series of models were constructed in order to investigate the relationship between atomic and electronic structure and TMR property. Models with normal component interface of Fe/MgO/Fe magnetic tunnel junctions were calculated by first-principles discrete variational method (DVM) within the framework of local spin density functional theory. The SP and TMR ratio of Fe at interface of ferromagnetic layer as well as density of states are analyzed. Our research shows that the thickness of ferromagnetic layers effect much on electronic structure. The interface and surface Fe layers have different feature from that of interior.