Abstract: The ancient saline lake of the Xinjiang Kuqa depression deposits huge thick salt rocks, which is suitable tectonic setting for the potash salt ore development. The obvious density variation between the huge thick salt rocks and the wall rocks can form a large enough change of bouguer gravity anomaly on the earth's surface. The thickness change characteristics of deep salt rocks can be analyzed qualitatively in reverse by studying the change of the gravitational field. The secondary depression favorable for potash ore concentration can be circled by analyzing the thickness change characteristics and the geological and drilling data. This paper picks up the bouger gravity residual anomaly which reflects the salt thickness change of the target stratum, by taking corresponding data processing means. The salt thickness change inferred by the residual anomaly is fitted with that explored by drills, which achieves the purpose of looking for potash ore by gravity measures.