The short-offset transient electromagnetic method (SOTEM) is one of TEM devices with great detection depth and high detection precision. 1-D inversion is the main way of its data processing and interpretation. In this paper, a modified image source inversion scheme is proposed for SOTEM data. Studies indicate that the conversional image source inversion scheme is not completely applicable to the SOTEM and may yield resistivity estimates that are biased at early time region. In this study, all time apparent resistivity was used to modified the inversed resistivity at early stage and a good result was obtained. Synthetic data and an application case both prove the effectiveness of this scheme.