Xylanases　were　widely　studied,　however,　most　xylanase　producing　strains　were　found　in　the　land.　The　research　of　xylanases　frommarine　microorganisms　is　still　rarely　reported.　A　Bacillus　sp.　strain　B659,　which　was　previously　screened　in　water　samples　from　Fujian　Pingtan,　has　a　high　xylanase　yield.　This　study　focused　on　the　optimization　of　medium　components　and　fermentation　conditions　to　increase　the　production　of　xylanase　by　strain　B659.The　optimized　liquid　culture　medium　for　xylanase　production　was　6%　wheat　bran,　1%　bean　cake　powder,　10　mmol/L　K2HPO4,　with　initial　culture　pH　6.0.　The　optimized　medium　resulted　in　a　1.6-fold　increase　of　xylanase　yield.　The　innoculation　volume　of　8%　and　culture　volume　of　25　mL/250　mL　were　optimum　for　xylanase　production.　When　strain　B659　was　incubated　at　30　with　shaking　speed　of　230　r/min　for　30　hours,　the　xylanase　activity　has　a　0.7-fold　increase　than　before.　After　the　optimization　of　medium　components　and　fermentation　conditions,　the　xylanase　activity　reached　2　838　U/mL,　which　increased　by　3.4　times　totally.　©　2015,　Chinese　Institute　of　Food　Science　and　Technology.　All　right　reserved.