The development and application of the expert system for searching for magmatic copper -nickel sulphide deposits (CGES) are discussed in this paper. The system is mainly characterized by the organic use of integrated in geological, geophysical and geochemical information in the prediction of hidden copper - nickel sulphide orebodies and aimed at increasing the percentage of hits in the prognosis. In the expert system one may find the authors' originality in using the logical inference of polyvalues and comprehensive and domain knowledge. The expert system has yielded good results. For example, orebodies of economic value have been encountered by two holes designed for checking the system on the Xiangshan intrusion in Hami, Xingjiang.