Abstract: Conventional VSP offset correction is a method based on the premise of underground medium isotropic homogeneity, using distance relationship among wellhead, shot point and observation depth location to correct longitudinal time deviation caused by offset. With increase of anisotropy and decrease of observation depth, the corrected time error given by this method may increase and can not meet the requirement of the user on the VSP data accuracy. In this paper, a new offset correction method with the goal of horizontal homogeneous degree of reflection two?way travel time is presented, using the mid?value of travel time?depth curve before and after conventional correction to correct the time of VSP time?depth relationship. The case study shows that this method can improve the accuracy of the time?depth relationship, with error reduced more than 50% of the time. In addition, the geologic horizon calibration combined with time?depth curve can be used to quantitatively determine the intervals affected by the offset through determination of the critical travel time and critical depth,thus realizing more reasonable use of VSP data