Accuracy calibration is a key of the vision alignment system of a high-precision chip mounter,which affects the precision and quality of the chip mounting greatly. For improving the calibration accuracy of the alignment system, this paper presents a new calibration method based on a grating.With proposed method, a group of data similar to quasi-sinusoid signals is abtained by calculating the sum of gray-value of pixels in each column.Then, these calculated data are elaborately converted into a Lissajous figure by pixel translation. The size mapping coefficient between the grating groove and their image pixels of the optical alignment system is calculated to realize the accurate calibration, obtained calibration results indicate that it is coincident with the theoretical calculation results well. A big standard ruler is used to verify the calibration experiment,the error analysis on the experimental data shows that the accuracy error by proposed method is less than 0.2 μm,which can meet the precision needs of vision alignment systems of automatic chip mounters.