Abstract: Keshen 3D seismic area is located in the eastern Kelasu tectonic belt of Kuqa depression, whose surface topography is high and steep with intense fluctuation and complex underground structure, leading to the low signal-to-noise ratio of seismic data and large errors in prestack time migration processing. In order to improve the image quality of target zone and make contact relationship more clear, prestack depth migration is performed. But limited by the precision of the prestack depth migration model, the structural configuration obtained from prestack depth migration processing is different from the actual one. A velocity model of prestack depth migration is proposed to improve the accuracy of structure mapping, which can be used to convert the prestack depth migration data to time domain. Meanwhile, 3-facies fusion velocity analysis of lithofacies, seismic facies and stress facies is carried out. Finally, variable velocity mapping is used to identify complex traps. This method have some advantages such as accurate depth migration data homing, high accuracy of 3-facies fusion velocity field and mature variable velocity mapping technique etc., which can improve the precision of trap identification. The actual drilling data has proved the identified traps in the Keshen 3D area. The study lays a foundation for oil and gas discovery and exploration in the mountain areas of the Kelasu tectonic belt. Keywords: