In this paper, a series of centrifuge tests was carried out to investigate the behaviour of geosynthetic- reinforced soil (GRS) walls under failure conditions. The development sequence of the slip surface (i.e., failure process, failure mode) and wall facing displacement were observed and discussed. The test results revealed at pre-failure stage, excessive settlement occurred close to the wall crest, and a distinct subsidence developed at the top of the wall at the end of the reinforced zone. At the moment of failure, wall deformation suddenly increased, and the wall collapsed instantly. Under serviceability conditions, a ranged factors of safety (FSs) from 1.5 to 2.5 for the wall deformation was found based on the established relationship between the factor of safety and wall facing displacement. The normalized horizontal deformation (Δx,max/H) at the wall face reached 8% to 12% at incipient wall failure. Compared with the wall deformation data in the literature, the global reinforcement stiffness was observed to have a significant influence on the maximum horizontal facing displacement of GRS walls at failure.