Residual hills landforms were developed in Northwest China. In lights of the above unique natural landscape and geological settings, the authors presented the geological properties of a place in Alashan of Northwest China as a study case, extracted the related geochemical anomalies with conventional methods of statistical method, trend surface analysis and moving average method. And a comprehensive contrast was conducted in combination with the available information on geology and mineral resources, proper method of geochemical anomaly extraction in semi arid region of Northwest China was discussed in this paper.