The　mechanism　of　tungsten　(W)　blistering　under　deuterium　(D)　plasma　exposure　is　still　under　investigation.　To　clearly　demonstrate　the　microstructure　and　nucleation　mechanism　of　blistering　on　W　exposed　to　D　plasma,　special　recrystallized　W　disc　samples　were　prepared　and　electropolished　with　back-thinned　method　for　TEM　observation.　D　plasma　exposure　(2.0　x　10(26)　D　m(-2),　573　K)　brought　it　numerous　intra-granular　blisters　and　protrusions　on　W　with　typical　orientation　dependence.　TEM　observation　revealed　the　intra-granular　blister　microstructure　that　substantial　dislocations　were　generated　on　the　center　and　edge　of　blister　via　severe　plastic　deformation　of　blister　cap.　Dislocation　tangles　formed　by　dislocations　from　blisters　were　revealed　and　supposed　to　be　the　nucleation　of　intra-granular　blister.　By　using　the　g.b　=　0　and　g.b　x　u　=　0　criterion,　＜　001　＞　dislocations　with　edge　component　were　identified　which　were　generated　by　＜　111　＞　edge　dislocation　interaction　in　dislocation　tangles.　A　{001}＜　001　＞　edge　dislocation　nucleating　and　blistering　mechanism　based　on　previous　works　is　proposed,　and　by　applying　which　blistering　in　recrystallized　W　could　be　well　explained.　Dedicated　experiments　demonstrated　that　intra-granular　blister　formation　depends　on　local　dislocation　density　which　validated　the　mechanism.