The authors report a new method for fabricating submicron gratings on curved substrates by combining thermoforming and nanoimprint technologies. A preshaping film was used to provide uniform pressure distribution throughout the whole concave substrate with the diameter of 60 mm and the radius of curvature of 92.5 mm. The concave glass could be resin coated uniformly by a conventional spin coater through the support of a soft holder. Either the preshaping film or the soft holder could be a buffer layer to prevent the curved glass from crumbling, which may result from high gas pressure during the imprint process. As for demonstration, a Rowland circle type concave grating with a period of 1.2 mu m was made, and the measured first order reflectance was about 20% at various wavelengths. (C) 2008 American Vacuum Society.