Fe-based bulk metallic glasses have the advantages of high strength and low coercivity. However, their plastic deformationability is negligible. Therefore, in this study, Sn was added to a Fe–Si–B–P bulk metallic glass matrix to study its influence onthe formation and plastic deformation ability of Fe–Si–B–P bulk metallic glasses. The results showed that the mixing enthalpyof Sn was less than that of Fe and other metal-like atoms, which caused Sn atoms to separate from Si-, B- and P-centeredclusters, resulting in metal-like clusters not occupying adjacent positions and the voids between clusters being occupied bySn atoms. With increasing Sn, the metal-metal bonds of the linked clusters increased and the macroscopic performance wasmanifested in an improvement in the plastic deformation ability. With 0.3 at% Sn addition, the alloy system showed the bestplastic deformation ability increasing from 0.7 to 2.2% and the yield strength of 3150 MPa.