The invention discloses a measurement method of a pattern on a mask plate. By means of the method, change of the pattern on the mask plate can be accurately detected, so that the alignment accuracy of the following epitaxy technique on a wafer is improved. According to the scheme, the pattern part on the mask plate is divided into small areas, a plurality of mask signs are formed in the line and row directions among the small areas, shape change of the pattern part on the mask plate can cause change of the sizes of the mask signs, and a photodetector can accurately detect change of the sizes of the mask signs. The change of the sizes of the mask signs can be accurately detected by the photodetector, the effect of accurately detecting change of the pattern on the mask plate is further realized, and the detection method is simple and effective; the mask signs are formed on a sign layer of the mask plate with an etching process or the mask signs are formed by forming multiple holes in a substrate on the wafer with a patterning technique, so that the photodetector can more accurately detect the mask signs, and the measurement method has huge practical value and promotional value.