Diffracted wave- front quality is one of the most important performance indexs for ruled gratings. For mechanically ruled gratings, positioning accuracy of the groove directly affects the wave- front quality of the gratings. The mathematical relationship between the inherent errors of the ruling machine which including the error of groove position, error of yaw and wave-front error of the gratings is developed, and the impact of various errors on the wave- front quality is analyzed. According to the error of groove position and error of yaw, a measure optical path is designed based on double-frequency laser interference, and a method to correct the error of groove position and error of yaw is proposed using piezoelectric actuator. According to the correction method, a double workbench is designed, and the ruling experiments for the size of 80 mm × 60 mm and groove density of 194 line/mm are carried out. The results show that the diffracted wave-front error of the ruled grating is reduced from 0.23λ to 0.093λ (λ = 632.8 nm) , and testing quality of the groove by atomic force microscope meets the requirement of the theoretical design.