Starting from unstable phase-shift formula of wavefield continuation and based on the perturbation theory, the authors derived a high-order form of wave equation generalized screen pre-stack depth migration operator equation by utilizing gradual spreading of single square root operators. Aiming at the instability for the calculation items of scattered wavefield in lateral variable-velocity media, the authors proposed an effective way to improve the stability by math approximation, and applied it to the wavefield recursion extrapolation. Then a stable seismic migration imaging method of high precision screen operators was obtained. The results show that the method has higher precision, which is better for the imaging of wide-angle information.