Abstract:One-pass 3-D migration can be achieved by using phase shift plus interpolation.The deformation of downward continuation operator in 3-D migration allows the uses of big step size in downward continuation and fast Fourier transform in image.What is more,the continuation step size can be automatically adjusted according to formation variation,thus greatly improving the computation efficiency.The application of phase shift plus interpolation to one-pass 3-D mig-ration causes neither the frequency dispersion nor the error that is incurred by migration operator splitting in x-y direction;therefore,the method is applicable to the situation where velocity varies vertically and laterally.It is illustrated that the method is one-pass3-D migration technique that can nicely cope with complicated steep geology structures.