Abstract: Alunite,which is the gangue mineral of Zijin gold-copper deposit,is the main object of study in this paper.On the basis of the field geological survey work,the mineralogical characteristics of alunite has been studied by systematic work of petrography and mineragraphy and chemical compositions of alunite has been researched systematically on application of electron microprobe,we obtain that the chemical composition of alunite of Zijin gold-copper deposit is of the characteristics that much lower K,S and higher Al in major elements and higher Cu,Ga and As in trace elements compared with theoretical value,and different forms of alunite is is of different chemical composition.Alunite,as is a kind of potassium resource,can be exploited in sorting development process.And,Ga,which is a rare element,has has some prospects in industrial application as associated elements.Besides,Cu can be exploited as a kind of low-grade Copper ores.