Lepidolite　is　a　kind　of　low-grade　lithium　ore　(3.5–4.0%　Li2O)　which　contains　more　than　22%　Al2O3　and　8%　K2O.　Removal　and　utilization　of　the　Al　and　K　will　be　very　important　for　the　economic　extraction　of　lithium　from　this　ore.　In　this　paper,　a　novel　method　is　proposed　to　remove　Al　from　the　leaching　solution　of　lepidolite　by　adding　ammonium　from　(NH4)2SO4.　The　results　indicate　that　adding　NH4+　could　remove　more　aluminum　and　have　a　smaller　loss　of　lithium　in　comparison　to　adding　K+　for　removing　aluminum　in　the　leaching　solution.　The　Al　removal　reached　up　to　80.44%　at　(K+ + NH4+)/Al3+　molar　ratio　of　0.95,　while　the　amount　of　Li+　(99.84%)　still　remained　in　the　leaching　solution.　In　addition,　the　phase　equilibrium　in　the　quaternary　K2SO4-Al2(SO4)3-(NH4)2SO4-H2O　system　at　278.2 K　was　investigated　to　support　the　above　conclusion.　The　results　verify　that　the　addition　of　ammonium　could　remove　more　Al3+　by　easily　forming　potassium　alum　(KAl(SO4)2·12H2O)　and　ammonium　alum　(NH4Al(SO4)2·12H2O).　©　2016,　The　Minerals,　Metals　&　Materials　Society.