A green, simple and economical route based on an efficient Bombyx mori silk fibroin assisted hydrothermal process has been developed to synthesize monodisperse hematite (alpha-Fe2O3) nanostructures with fine shape control. The effects of reaction time and silk fibroin concentration on the morphology of alpha-Fe2O3 have been investigated systematically. Several morphologies including quasi-nanocubes, nanospheres that are composed of primary nanoparticles, and the coexistence of nanospheres and primary nanoparticles were obtained by varying the silk fibroin concentration. The formation mechanism of different alpha-Fe2O3 morphologies are discussed based on the silk fibroin template effect. In addition, these alpha-Fe2O3 nanostructures exhibit interesting shape-dependent magnetic properties. We believe that such a synthesis method of alpha-Fe2O3 provides an efficient shape control and cost-effective approach that is potentially competitive for scaling-up industrial production.