The invention relates to a time-domain seismic
waveform inversion method by utilizing variable-step-length grid
acoustic wave field simulation in the field of seismic data depth modeling. The method is characterized by carrying out
subdivision by utilizing a variable-step-length grid in
continuation depth direction; increasing calculating grid points on grid diagonals of a star
convolution operator; obtaining an accurate relational expression of a
wave field evolved with the time in a time-wave number domain; calculating
convolution coefficients of the grid points according to
wave field propagation speed of spatial points and time
continuation step length to enable the error of wave number domain
time evolution relationship corresponding to each point to be minimum; in the
simulation space range, establishing speed indexes and calculating
convolution operators corresponding to the speeds; and carrying out
wave field forward
simulation by utilizing the convolution operators and the speed indexes to enable error of a
seismic wave field recorded in the field and a
seismic wave field obtained through forward
simulation to be reduced, and iteratively updating a speed model and finishing inversion. The method solves the problem of poor precision of
time derivative approximate calculation caused by an existing
algorithm and solves the problem of heavy wave
field simulation calculation burden and low calculating efficiency.