The development of cost-effective preparation routes for high-quality graphene is important for its large scale application. Here, we propose an one-step scalable preparation method of few-layer graphene (FLG) by the exfoliation of flake graphite in a novel binary-component system comprised of peroxyacetic acid and sulfuric acid. This provides a similar to 100% yield of FLGs from the starting graphite in 4 h at room temperature. The as-prepared FLG sheets behave a few-layer feature (average layer number < 5 layers) and possess large areal sizes (the maximum areal size can be up to 420 mu m(2), average sheet areal size is 190.8 mu m(2)). Furthermore, the resulting FLG also exhibits a high quality with few structure defects (the oxygen content is only 1.2%) and thus possesses a superior electrical conductivity of 1.46 x 10(5) S m(-1). The present method shows great promise for the mass production of high-quality graphene sheets.