The method of realizing optical wavelet transform (OWT) with Mexican-hat wavelet function for diffusion-limited aggregate (DLA) pattern is described in this paper. DLA fractal pattern is successfully dissolved into different scale patterns by using a series of discrete dilation factor. The advantage of optical wavelet transform (OWT) is that the constructing process of self-similarity in fractal pattern can be observed simply and rapidly from the domain of different time. DLA Fractal dimension has been also obtained using the method of the OWT in this paper. The experimental results have proved that OWT is an important method to analyze DLA pattern in real time.