Abstract:The paper expounded the development of seismic migration technique from two aspects: principle and technique,analyzed the differences of different migration techniques and presented three expressions of imaging conditions. On the basis of expounding model-building technique of prestack depth imaging velocity,the paper presented following basic principles that the velocity model building should follow:(1)it should choose the events having good continuity, the thickness of beds should not be too thin and differential interval velocities of ad jacent layers should greater than 10%; (2)it can ad-equately reduce the interpretation of target lines in gentle parts of structures and increase the interpretation of target lines when the structures are complex;(3)it should make modification of interval velocities according to picked time horizons in ordinary migrated sections, making efforts to keep smooth variation of interval velocities both in vertical and in lateral directions and align the CRP gathers. It was showed by the applied cases of prestack depth imaging technique in Hailar area that the effects of prestack imaging technique are significantly superior to that of poststack migra-tion.