Ti-MWW　molecular　sieve　catalyst　were　prepared　by　hydrothermal　synthesis　and　acid　treatment.　Epoxidation　of　allyl　alcohol　(AAL)　by　H2O2　over　Ti-MWW　molecular　sieve　catalyst　was　studied　using　water　as　solvent.　The　lower　concentration　of　allyl　alcohol　helped　increase　reaction　rate　and　higher　concentration　of　H2O2　decrease　selectivity　to　glycidol.　Under　suitable　conditions;　reaction　temperature　333　K,　reaction　time　30　min,　Ti-MWW　molecular　sieve　catalyst　dosage　50　mg,　allyl　alcohol　10　mmol,H2O2　10　mmol,　and　H2O　20　mL,　conversion　of　allyl　alcohol　and　selectivity　to　glycidol　could　reach　96%　and　98%,　respectively.　Selectivity　to　glycidol　was　the　highest　when　n(　AAL)　:　n(H2O2)　=　1,　but　dropped　quickly　if　reaction　temperature　increased　above　333　K.　The　reaction　mechanism　was　similar　to　that　of　alkene　epoxidation　on　TS-1　molecular　sieve　catalyst,　which　involved　a　transition　state　of　a　5-membered　ring　formed　through　a　solvent　molecule　or　an　allyl　alcohol　molecule　on　Ti　active　site.　High　selectivity　to　glycidol　was　attributed　to　high　structural　stability　of　Ti　species　and　nature　of　the　5-membered　ring.