In this paper the scaling behavior and percolation structure of spinodal phase separation in a binary polymer blend of poly (vinyl acetate) (PVAc) with poly(methyl methacrylate) (PM-MA) were studied by using light scattering and optical microscope techniques. Unmixing process was found to give the scaling law on the wave number of the dominant Fourier componen' of the fluctuation qm and on the maximum scattered intensity Im as given by qm-t-α and I-tβ The percolation structure was found in the phase separation process. The fractal dimension for 2d cluster of the spinodal decomposition can be obtained from microscope picture.The fractal dimension is about 1.64.