Recently, the S receiver function method has been successfully developed to identify upper mantle interfaces. S receiver functions have the advantage of being free of s-wave multiple reflections and can be more suitable than P receiver function for studying mantle lithosphere. However, because of specific ray geometry of the S-to-P converted waves, the S receiver function method has some technical difficulties and limitations. We selected data from teleseismic events (Mb>5.7, epicentral distance between 60?- 85?) recorded since 1996 to present at 8 three component short period stations from the Tabriz Telemetry Network. Clear negative signals from the lithosphere-asthenosphere boundary (LAB) are observed. The average LAB depth is approximately 85 Km and varies from 77 to 103 km underneath the NW of Iran.