Abstract: Recovering the erosion thickness of the formation is one of the foundations for basin quantitative analysis.Here we estimated the erosion thickness of the Es4(the fourth member of the Shahejie Formation)and Ek(Kongdian Formation)strata in the Jiyang Depression by means of computer modeling,based on the improved sonic time difference principles,and combined with the optimizing porosity algorithm.The stratigraphic contrast method on seismic profiles is combined to estimate the erosion thickness for the places where the sedimentation regularities of removed formation are destroyed heavily.This traditional method is also improved in this paper.The final erosion thickness of formation is obtained by the weighted average of variously calculated results abtained by using multi-perspective stratigraphic contrast method,so that the calculation errors could be significantly reduced.Our results show that the erosion exists pervasively in the Es4 and Ek strata of the oilfield with a relatively smaller intensity,and the relatively larger erosion is found in the fringe of the sag.The erosion amount of the Es4 ranges of 50～300 meter,with the average of 150 meter;The largest one exists in the edge of western sag of the Luxi Uplift reaching a value of approximately 1000 meter, but localized in a relatively small area.The erosion amount of Ek is relatively larger than that of the Es4,usually varying from 150 to 400 meter,with the average of 250 meter.The largest one is found in the northeast rim of the Huiming sag,with the value of 800 meter.