Abstract: The chemisorption of hydrogen on the multilayer surface segregated Au-Ag alloy is investigated using Green function method and the multicoupling self-consistent coherent-potential approximation. The interaction between chemisorption and multilayer surface segregation is discussed in detail. The chemisorption-induced surface segregation can change greatly the surface component of the alloy as well as the chemisorption energy. For H/Au-Ag system, a fluctuation characteristic of the calculated values of chemisorption energy is found if increasing the number of surface layers to calculate.