In order to identify more new supernova remnants, astronomers are concerned about extracting useful signals from the observed data interspersed with various noises. The wavelet analysis is a newly developed time frequency analysis method. Like Fourier analysis, any function with finite energy can be expanded on the orthonormal wavelet bases. Unlike Fourier bases, wavelet bases have the property of compact support. This good property makes the wavelet method a very effective way for separating the local noi...