The alignment method of dual-grating Moiré fringe has characteristics of high-accuracy and reliability, which is mainly fit for contact and proximity lithography. For the realization of high-accuracy measurement, the parallelism between mask grating mark and wafer grating mark is practically required. Generally, mask grating mark imaged in CCD has a tiny inclined angle. Therefore, an improved method is proposed, based on the previously proposed calibration method for inclined fringes through phase slope. The improved method makes full use of phase information in directions of 45° and 135° to revise the imaging position of CCD. By this mean, the mask grating fringes are also calibrated. Through comparison between the two methods, the results imply that the improved method is provided with large-measurement scope, strong anti-noise and high-accuracy, and measurement accuracy is better than 0.001° level.