Abstract: Based on different spectra power of the different field source,we had studied the distribution characteristics of field source in north of Songliao Basin.In order to get the average depths of the different field source,bouguer gravity anomaly data from north of Songliao basin were calculated by the match-filter method.The bouguer anomaly can be divided into upper source field,middle source field,and lower source field,so we thought that there are three-layer crust structure in north of Songliao basin.The gravity anomalies produced by upper source field are large and make the biggest contribution to gravity prospecting. The gravity anomalies of middle source field and lower source field are both small,but they have a wonderful inheritance.After getting the average depth of field source,we also calculated the average interface depth between upper crust and middle crust by using Parker iteration inversion method,found there is 'upwelling area-sediment basin-upwelling area' tectonic characteristic at the density interface.