The　research　of　perovskites　optical　properties　is　of　great　value　for　dual　wavelength　lasers.　However,　the　phenomenon　of　double　peaks　in　perovskites　photoluminescence　(PL)　has　not　been　explained　systematically,　which　makes　the　optical　research　of　perovskites　still　a　challenge.　In　order　to　have　a　deep　understanding　of　the　optical　properties　and　applications　of　new　perovskite　materials,　this　phenomenon　of　MAPbX(3)　(X　=　I　inverted　exclamation　,　Br　inverted　exclamation　)　is　explained　in　this　paper.　The　structural　characteristics　of　the　materials　were　investigated　by　XRD.　We　found　that　there　were　PbBr2　defects　in　MAPbBr(3)　and　orthorhombic　structure　defects　in　MAPbI(3);　By　calculating　the　energy　level　distribution　of　perovskites　and　defects,　the　PbBr2　in　MAPbBr(3)　and　orthorhombic　phase　structure　in　MAPbI(3)　can　introduce　a　new　energy　level　into　crystals　and　these　two　structures　lead　to　the　PL　peaks　of　542　nm　and　771　nm,　respectively.　It　is　the　surface　defects　in　MAPbBr(3)　and　multi-structures　in　MAPbI(3)　that　leads　to　the　two　peaks　phenomenon　of　perovskite　photoluminescence.　All　the　work　explained　the　mechanism　of　perovskites　PL　double　peaks.　This　study　can　provide　theoretical　reference　for　perovskites　researches　and　experimental　references　for　new　materials　and　a　promising　pathway　for　dual-wavelength,　practical　laser　based　on　perovskite　crystals.