In　this　study,　two　laboratory-scale　simulated　landfill　bioreactors　were　established,　of　which　Reactor　A　was　operated　only　with　leachate　recirculation　and　served　as　the　control,　and　Reactor　B　was　operated　as　semi-aerobic　bioreactor　landfill　with　leachate　recirculation.　In　situ　leachate　treatment　and　accelerating　organic　decomposition　in　semi-aerobic　bioreactor　landfill　was　investigated.　The　results　indicated　that　the　introduction　of　air　into　the　landfill　was　favourable　for　optimising　the　micro-organism　growth　environment　and　accelerating　the　degradation　of　organic　matter.　It　can　be　seen　clearly　from　the　results　that　NH4+-N　can　be　removed　in　situ　in　the　semi-aerobic　bioreactor　landfill　with　leachate　recirculation.　Moreover,　semi-aerobic　bioreactor　landfill　showed　lower　emissions　for　leachate　than　those　in　leachate　from　anaerobic　landfill,　with　low　concentrations　of　COD,　VFA,　NH4+-N　and　TKN,　and　which　saved　the　disposing　process　of　the　discharged　leachate.　The　three-dimensional　excitation-emission　matrix　fluorescence　spectroscopy　(EEMs)　of　dissolved　organic　matter　(DOM)　in　Reactor　B　changed　greatly,　and　fluorescence　peak　changed　from　protein-like　fluorescence　at　Day　60　to　humic-like　fluorescence　at　Day　95　and　250,　while　in　Reactor　A,　fluorescence　peak　of　DOM　was　always　protein-like　fluorescence.　The　comparison　of　the　EEMs　indicated　that　the　semi-aerobic　landfill　accelerated　the　organic　decomposition.