Abstract: We apply discrete wavelet transform and continuous wavelet transform to do some simulation experiments of separating causative body and determining the depth of field source,and find that wavelet transform is effective to identify depth of source.What's more,we have researched depth character of the Ryukyu subduction zone based on real gravity anomaly data,and presume that the subduction zone curves to horizontal at about 105km underground at 122.5 degrees east longitude line.