Based on a study of the regularity governing the distribution of geochemical background fields of such regional characteristic elements as Fe,Mg,Si,K,Sb,Hg and U in 1:200 000 Xiaoergou sheet of Da Hinggan Ling shallowly-covered region, the authors have made a useful discussion on such basic geological problems as boundaries of geological bodies, faults and concealed rock bodies. Field inspection shows that the application of regional geochemical characteristic elements to the study of basic geological problems is effective and seems likely to play an important role in conducting regional geological mapping and improving as well as accelerating geological mapping.