The invention relates to a post-stack earthquake wave impedance inversion method and belongs to the technical field of geophysical exploration. The method comprises the steps of: extracting earthquake wavelets by means of data processing; establishing well-earthquake time depth relations of all wells in a work area to be inversed; calibrating the reflection position of each lithologic interface on an earthquake profile; generating wave impedance curves of time domains of all the wells, and carrying out decompaction correction on the wave impedance curves; establishing a geological construction framework model and an earthquake wave impedance inversion initial model of the work area to be inversed; and finally carrying out post-stack earthquake wave impedance inversion on the earthquake wave impedance inversion initial model of the work area to be inversed, and obtaining a decompaction wave impedance inversion result. The post-stack earthquake wave impedance inversion method effectively eliminates the lithology identification multi-solution influence of a compaction effect of stratum deposition on the earthquake wave impedance, the wave impedance data obtained by inversion can practically and vertically reflect the stratum deposition rhythm changes and can practically and transversely reflect the lithology changes, so that the exploration disposition of an oil field is well guided.