Rate　coefficients　of　H　atom　abstraction　and　H　atom　addition　reactions　of　3-hexene　by　the　hydroxyl　radicals　were　determined　using　both　conventional　transition-state　theory　and　canonical　variational　transition-state　theory,　with　the　potential　energy　surface　(PES)　evaluated　at　the　CCSD(T)/CBS//BHandHLYP/6-311G(d,p)　level　and　quantum　mechanical　effect　corrected　by　the　compounded　methods　including　one-dimensional　Wigner　method,　multidimensional　zero-curvature　tunneling　method,　and　small-curvature　tunneling　method.　Results　reveal　that　accounting　for　approximate　70%　of　the　overall　H　atom　abstractions　occur　in　the　allylic　site　via　both　direct　and　indirect　channels.　The　indirect　channel　containing　two　van　der　Waals　prereactive　complexes　exhibits　two　times　larger　rate　coefficient　relative　to　the　direct　one.　The　OH　addition　reaction　also　contains　two　van　der　Waals　complexes,　and　its　submerged　barrier　results　in　a　negative　temperature　coefficient　behavior　at　low　temperatures.　In　contrast,　The　OH　addition　pathway　dominates　only　at　temperatures　below　450　K　whereas　the　H　atom　abstraction　reactions　dominate　overwhelmingly　at　temperature　over　1000　K.　All　of　the　rate　coefficients　calculated　with　an　uncertainty　of　a　factor　of　5　were　fitted　in　a　quasi-Arrhenius　formula.　Analyses　on　the　PES,　minimum　reaction　path　and　activation　free　Gibbs　energy　were　also　performed　in　this　study.