The main residual aberrations of Rowland circle mounts are astigmatism and sagittal coma, which seriously deteriorates the throughput and spectral resolution. An analytic study on the aberration property of a Rowland circle mount which is recorded with the off-Rowland recording geometry is presented. It is found that the astigmatism and sagittal coma can be simultaneously eliminated for two wavelengths, between which the aberrations are both greatly reduced. The Rowland-circle mounts used for broad-band spectrographs can be optimized by properly choosing the using geometry and correction wavelength. A grating working in the wavelength range of 160~600 nm is designed and compared with a conventional grating. The result indicates that significant reduction of the astigmatism and improvement of resolution are both achieved over a wide wavelength range.