The multilevel diffraction spectrum of target image on the filtering plane produced by the periodic structure of Space Light Modulator(SLM) in Vander Luget Correlator(VLC) was obtained.In order to increase output correlation peak value,matched filters can be loaded at the positions of different diffraction spectra on the filtering SLM at the same time to perform matched filtering of multilevel diffraction spectra.Theoretical analysis results indicate the correlation spots from different diffraction spectrum outputs are at the same position of the output plane,and the correlation peak value is improved with coherent superposition of multilevel correlation spots.The experimental results show that the mean output correlation peak value by performing matched filtering for multilevel diffraction spectra of target image has increased about 32% than that of zerolevel spectrum.The output correlation peak value can be effectively increased using this method.