In Tahe area,large-sized caves and fissure-caves are the main reservoir space types,which are characterized by complex geological characteristics and rapid change in lithology.The seismic response of these kinds of reservoirs is diffraction whose precision of images has a great impact on the reservoir prediction.Based on the scattering theory,the equivalent offset method (EOM ) can obviously improve the precision of diffraction imaging.The equivalent offset prestack migration method and its parallel method were introduced,and a model case was used to illustrate the efficiency of EOM.At last,this method was applied to the real data migration processing in Tahe area.A comparison with the conventional PSTM method shows that,in the EOM profile,the focusing of the carve-fracture diffractions,the images of faults and breakpoints and the lateral resolution have been improved.