This paper analyses feature of I, S, CI, Sr geochemical field data which correlated oil and gas geochemical ex- ploration in soil samples of Songliao basin, and operated in traditional method and fractal method to determine other anomaly lower threshold, then delineated geochemical anomalies regioru Through comparing, it is found that the results using fractal method are better, which avoid to omission oil and gas information, and reject some interference factors.