This paper presents a method of intensity thresholding for the laser speckle patterns of multi gray levels (for example 256 levels). After this thresholding operation, the main features of the spacial frequency power spectral density of laser speckle intensity are maintained and the amount of computer digital storage space can be reduced greatly. An optimum threshold level is found that minimizes distortion of the power spectrum for speckle data of the circular and ring apertures.