Abstract: In the past the emphasis of the study of wall-rock alterations is mostly on the field of gitology. People only made an isolated study on a certain deposit, and few regional-scale systematical studies were made. The study method proposed in this paper is as follows: wall-rock alterations are regarded as information for mineral prospecting and mathematic statistics is conducted according to the amount of occurrences of the alterations, their intensity and the features of the altered mineral association; then one delineates districts of wall-rock alteration intensity, finds the probability of occurrence of each alteration in the survey area and prospect, ascertains the altered mineral association genetically related to main useful minerals in the survey area, and changes the previous qualitative study into the quantitative one. The wall-rock alteration intensity districts delineated through preparation of the isopleth map of wall-rock alterations often yield almost the same prospecting results as the physical and chemical anomalies and heavy placer mineral anomalies. Thi work needs less costs because the primary information it requires can be collected by the way in the traverse survey. Its economic and social effectness are outstanding.