Structural, electronic, and magnetic properties of the Fe(310) surface are studied using first-principles full-potential linearized augmented plane wave method within the generalized gradient approximation. Sizable multilayer relaxation is found to extend to the seventh layer from the surface. While low-energy electron diffraction (LEED) and first-principles calculations on multilayer relaxations generally agree for low-index surfaces, there is a disagreement for this high-index surface. We conjecture that this disagreement might be due to the small data set and variational freedom in the LEED analysis. The spin magnetic moment of the Fe(310) surface and subsurface atoms is enhanced to 2.85μB and 2.65μB, from a bulk value of 2.23μB. The surface layer enhancement is smaller than that in Fe(100) and larger than that in Fe(111), although all three surfaces have the same coordination number. Subsurface layers are found to play an important role in the magnetization of the surface atoms in the case of an open surface, where the vacuum affects more atomic layers.