Abstract: Aohan County is located in the thick loess covered area of Chifeng region, Inner Mongolia. The 1:50 000 regional geochemical investigation in the area involves mainly stream sediments sampling, supplemented by soil sampling. The study is carried out by using -10-+60 mesh granularity of stream sediment samples and -10 mesh granularity of soil samples in loess covered area. However, due to different sampling media, which represent different chemical significances, there are system errors in testing. In this paper, the experimental results of different media are calculated divisionally, taking Au for example, to determine the background values of different sampling areas. In addition, different methods are adopted to correct the system errors between soil and stream sediment samples, in order to meet the need of anomaly analysis and avoid omitting the low weak anomalies as far as possible. The three methods weaken the anomalies of loess covered area in some degree, although the stream sediment anomalies are confirmed. The standardized method causes a less weakening to the anomaly, which is most close to the geochemical information of loess covered area; while the correction methods of contrast transformation and median transformation reflect weaker geochemical information.