Structural, electronic and magnetic properties of FenPt55-n nanoparticles have been systematically studied based on the density functional theory. Firstly, the results show that surface Fe fraction has the same change tendency with excess energy and the nanoparticles have high stability when surface Fe fraction is small and excess energy is low. Secondly, analysis of Bader charge illustrates that the charge transfer reaches the maximum with Pt/Fe atomic ratio of 1:1. Thirdly, total magnetic moments of FenPt55-n nanoparticles increase with the increasing of Fe composition. Pt atom at the center site has promotion effect on the total magnetic moments of FenPt55-n nanoparticles, while Pt atom at the sublayer or outmost layer has inhibition effect. For the atomic magnetic moment, Fe atom occupying the edge of vertex in the second shell site (the center site) has maximum (minimum) atomic magnetic moment. (C) 2015 Elsevier Inc. All rights reserved.