The free-energy concentration expansion method (FCEM) is introduced and applied to the elucidation of short-range order (SRO) effects on surface segregation in alloys. This statistical-mechanical analytical approach, based on the Ising model Hamiltonian energetics, is verified by Monte Carlo (MC) simulations. In particular, calculations performed for the (100) surface of fcc solid solution show that the FCEM agrees with MC results much better than the Bragg-Williams (BW) theory, including the prediction of an increase in equilibrium segregation level with temperature, associated with SRO/segregation competition. FCEM is quite accurate and simple to apply, demanding much less computational effort compared to MC simulations or the cluster variation method. It can replace the corresponding BW formulae in theoretical evaluation of various surfaces as well as bulk phenomena, allowing systematic studies of SRO effects in alloys.