In order to find the favorable section of petroleum in the Southeastern of Keshiketeng, Inner Mongolia, based on 1:200 000 stream sediment survey, the anomaly threshold of element was determined, and the geochemical anomaly figures of single element were drawn by the means of background mean value plus double standard deviation. The element anomalous characteristics of iron group elements, high-temperature elements and low-temperature elements were analyzed, element combination anomalies were found, and then the potential favorable sections of petroleum were discovered. The results showed that ring anomaly zones with high values of iron group elements existed in Wufendi-Tuchengzi-Chifeng-Beishierjiazi area~ the geochemical low background area developed in the zone restricted by the ring anomaly~ characteristics of element anomaly distribution of high- temperature and low-temperature elements were opposite to that of iron group elements, and elemental geochemistry was high in the geochemical low-background area of ring anomaly zones with high values of iron group elements~ geochemistry of Hg, which was good indicator for petroleumreservoir, was high anomaly in the geochemical high-background area. Therefore, it was possible that petroleum reservoir existed below the geochemical low-background area of ring anomaly zones with high values of iron group elements, which was favorable section to explore the petroleum.