Halide　perovskite　materials　are　considered　a　promising　optical　gain　medium　for　stimulated　emission　and　have　aroused　tremendous　interest　in　the　field　of　laser　research.　The　development　of　low-threshold　optically　pumped　amplified　spontaneous　emission　(ASE)　is　critical　for　the　advancement　of　continuous　wave　(CW)　and　electrically　pumped　micro-nano　lasers.　In　this　work,　an　efficient　ZnS　additive　is　incorporated　into　the　FA0.85MA0.15PbI2.55Br0.45　perovskite　films　to　diminish　the　ASE　threshold　and　extend　the　photostability　by　the　dual-site　synergistic　passivation.　The　experimental　measurements　and　first-principles　calculations　based　on　the　density　functional　theory　(DFT)　are　employed　to　elucidate　the　doping　mechanism.　The　designed　ZnS-based　perovskite　films　yield　a　mitigated　ASE　threshold　of　8.5　mu　J　cm-2　with　an　elevated　optical　gain　coefficient　of　109.06　cm-1,　which　outperform　those　of　the　control　films　(12.7　mu　J　cm-2　and　74.10　cm-1).　The　in-depth　experimental　characterizations　and　theoretical　calculations　have　corroborated　that　the　improvement　of　ASE　performance　can　be　ascribed　to　the　dual-site　synergistic　passivation　effects　of　Zn2+　and　S2-,　which　reduces　the　surface　defects　of　perovskite　films,　suppresses　the　nonradiative　charge　recombination　and　improves　the　optical　stability.　This　work　provides　a　resultful　strategy　to　construct　the　solution-processed　perovskite　lasers　with　low　thresholds　and　superior　stability.　Through　dual-site　synergistic　passivation　effects,　Zn2+　enters　the　lattice　as　interstitials,　and　S2-　fills　the　I/Br　vacancies,　which　synergistically　improves　the　perovskite　ASE　properties.　The　doped　films　show　a　longer　fluorescence　lifetime　and　better　stability　than　the　pristine　perovskite　films.　image