Through　the　technique　of　calculating　flow　dynamic　(CFD),　adopting　K-ε-2-equation　model,　the　numerical　simulation　of　the　flow　field　in　semi-dry　desulphurization　reactor　was　carried　out　to　study　the　influence　of　flue　gas　of　distributors　of　several　different　types　on　the　flow　field　distribution.　The　distribution　of　flow　field　changed　obviously　when　the　flue　gas　distributors　was　set　up　in　the　desulphurization　reactor.　Through　changing　the　structure　of　flue　gas　distributor　to　realize　the　even　distribution　of　vectors　of　velocity,　gradient　of　pressure　drop,　and　energy　in　the　desulphurization　reactor.　The　contact　rate　of　desulphurization　agent　with　SO2　was　increased　and　the　reaction　efficiency　of　desulphurization　reactor　was　enhanced.　The　study　results　supplied　the　basis　of　optimization　of　the　structure　of　desulphurization　reactor.