Abstract: Huahai basin is in the western edge of the corridor basin group in Gansu Province. Based on the results of soil gas radon concentration measurement and the background structural and evolution law of Huahai basin, the authors analyzed the characteristics of the abnormal fields by the Information Entropy Subinterval Area Median Contrast Filtering (SAMCF) Method. The results were different with the different m and n paraments by using SAMCF method. It also showed that the entropy varied from 2.5 to 3.6. The relationship of entropy and m and n was complexity. However, it varied like a "U" sharp with the incease of k parament. When the k varied from 15 to 20, the minimum entropy was gotten showing the western party of the study area with anomaly radon gas in the soil, is the favorable area for deep uranium exploration.