Joint　spacing　is　one　of　the　significant　factors　affecting　the　rock　fragmentation　by　TBM　cutters.　Based　on　laboratory　test,　the　effect　of　joint　spacing　on　the　fragmentation　modes　and　penetration　under　TBM　disc　cutters　is　studied.　In　the　test,　two　kinds　of　concrete　with　different　strengths　are　adopted　to　simulate　rock　sample.　The　joint　spacing　varies　from　50mm,　80mm,　200mm　and　the　intact　samples　are　also　tested　for　comparison.　Firstly,　four　kinds　of　fragmentation　modes　for　single-set　jointed　rock　are　found:　(1)　the　crack　initiates　from　the　joint　plane　and　propagates　to　free　surface,　to　form　fragmentation　chipping.　(2)　The　side　crack　and　median　crack　initiate　beneath　the　crushed　zone　and　propagate　to　joint　plane　to　produce　chipping.　(3)　In　the　rock　block　indirectly　indented　by　cutter,　the　crack　initiates　from　the　joint　plane　and　propagates　to　adjacent　joint　plane　to　produce　chipping.　(4)　Normal　fragmentation　mode.　Basically,　the　first　two　kinds　are　generally　for　jointed　rock,　while　the　other　two　kinds　are　respectively　for　the　jointed　rock　with　small　and　large　joint　spacing.　Secondly,　from　the　viewpoint　of　the　fragmentation　modes,　the　effect　of　joint　spacing　on　tunnel　face　stability　is　investigated　and　then　compared　with　field　data　of　Jinping　II　Hydropower　Station.　Finally,　it　is　shown　that　highest　penetration　rate　can　be　achieved　with　the　joint　spacing　of　50-80mm,　and　moreover,　joint　spacing　gives　more　notable　effect　on　fragmentation　of　the　rock　with　higher　strength.