Abstract: The vertical depth differential value between the real depth drilled in well Xihu-1 and the predicted depth is much less than the geophysical accuracy error range. According to this phenomenon, forward model which can show the regional structural characteristics of the southern margin of the Zhunger Basin has been constructed, and forward modeling analysis has been conducted. From the perspective of the critical state, the quantitative relationship between depth-domain and time-domain model has been analyzed in order to find out the inherent regularity in parameter changes caused by model coordinate system changes .The modeling results show that in the middle-deep structure, the deformation in time domain can not correspond to deformation in depth domain, and distortion factor existed. In complex structural superimposed areas, the velocity is characterized by low initial velocity, non-linear velocity variation. The velocity change has certain influence on structure, showing the regularity of "high put low pull".