The stability and magnetism in fcc single-crystal nickel nanowires with low-index axial direction are studied by first principles methods in this work. For fcc nickel nanowires, it is found that 110 is the most stable direction, while 111 is less stable and 001 the least stable. Nickel nanowires can be described by a simple core-shell model. The core atoms of nanowires have almost the same magnetic moment as in bulk metal. Surface atoms of nickel nanowires have larger atomic magnetic moments in varying degrees related to axial direction. In our calculated nanowires with low-index axial directions, surface atoms in 110 nanowires have lowest magnetic moments while those in 100 nanowires have the largest.