本文从三维波动方程出发，导出了用于三维叠后逆时偏移的无层间反射的波动方程，并给出了其数值算法和稳定性条件。通过对一系列二维及三维模型的偏移计算，证明了方法的正确性和有效性。与常规的深度外推偏移方法相比，它具有精度良好、计算量小、无倾角限制、避免了倏逝波能量以及能适应空间变速的一系列优点，是一种解决三维复杂构造成像的有效方法。 Based on the three-dimensional wave equation, this paper derives the wave equation without interlayer reflections for three-dimensional post-stack inverse time migration, and presents its numerical method and stability conditions. By calculating the offset of a series of two-dimensional and three-dimensional models, the correctness and validity of the method are proved. Compared with the conventional depth extrapolation method, it has a series of advantages such as good precision, small computation, no obliquity limit, avoiding evanescent wave energy and adapting to space velocity. It is a new method to solve 3D complex structure imaging Useful ways.