In this paper,tilt observation data of deformation has been calculated by using wavelet method of Mallat arithmetic,and the relation between gained result and seismic activity has been analyzed.The result indicates that the earth tilt data has obviously deformation abnormity before big earthquakes.Wavelet method has enlarged earth tilt abnormity in some frequency bands.So wavelet method gives us a strong tool in analysis of seismic precursor trend abnormity.