Microbeam analysis is a new technology applied in geology. Through microbeam analysis of minerals by means of electron microprobe the author obtained new evidence on the origin of ores which deepens the genetic theory on mineral deposits. Taking Au-Ag intergrowth compounds as an example this paper has reached the following conclusions. In the Au-Ag compounds of differem types of gold deposits as sequemially replaces Au, making up a continuous isomorphous series. The content of Au and Ag in native gold forms a regular pattern. The development of native gold and that of electrum have something to do with different types of gold deposits respectively. Abundances of trace elements in Au-Ag minerals are controlled by geological settings and geochemical fields. The above study provides new geological information and a new method for the study and exploration of gold deposits. 、