The　structural　characteristics　and　composition　of　alunite　in　the　Zijinshan　gold-copper　deposit　were　studied　by　infrared　absorption　spectroscopy　and　X-ray　powder　diffraction　analysis.　The　results　show　that　infrared　spectral　absorption　peaks,　the　growth　degree　of　crystal　faces　(006)　and　(004),　and　crystal　cell　parameters　of　the　alunite　display　gradually　decreasing　trend　from　the　crater　to　northwest　along　the　metallogenic　belt.　Combined　with　electron　probe　analysis　results,　we　go　further　and　obtain　that　the　alunite　mainly　belongs　to　potassium　alunite,　and　the　characteristics　of　infrared　spectra　and　XRD　of　the　alunite　mainly　have　relation　to　the　content　of　potassium　of　the　alunite　in　different　parts　of　volcanic　mechanism.　Near　the　crater,　with　higher　temperature,　it　is　helpful　for　the　isomorphism　replacement　between　sodium　and　potassium,　the　content　of　sodium　is　higher　and　the　content　of　potassium　is　lower　relatively　in　the　alunite;　and　away　from　the　crater,　the　temperature　is　relatively　lower,　it　is　against　the　isomorphism　replacement　between　sodium　and　potassium,　the　content　of　sodium　is　lower,　and　the　content　of　potassium　is　higher　relatively　in　the　alunite.