Abstract: To solve the imaging problems in complicated media, the author briefly discusses the principle of generalized screen migration, which is paid close attention recently in the circle of geophysicists. Based on the theory of scattering wave, this method is deduced by means of local Born approximation. It is implemented in dual (space and wavenumber) domain with high efficiency. Moreover, the generalized screen operator works in media with laterally varied velocity, and can image reflectors with steep dip accurately. Poststack depth migration results from numerical tests of synthetic data with strong varied velocity and field data show that the generalized screen operator has great application value in imaging the complex geological bodies.