To　study　the　influence　of　penetration　on　the　rock-breaking　efficiency　of　a　TBM　cutter,　a　linear　cutting　test　was　carried　out　for　Beishan　granite　utilizing　a　mechanical　rock-breaking　test　platform　and　17-inch　disc　cutters　with　a　constant　cross　section　and　an　80　mm　spacing,　during　which　the　penetration　was　divided　into　7　grades　from　0.5　mm　to　3.5　mm　at　an　interval　of　0.5　mm　and　the　sample　was　1000　mm×1000　mm×600　mm.　Through　the　test,　the　three-directional　force　applied　on　the　cutter　was　recorded;　the　rock　chips　were　collected　layer　by　layer;　the　influence　of　penetration　on　rock-breaking　efficiency　was　analyzed　based　on　the　variation　of　the　mean　normal　force,　mean　rolling　force,　specific　energy,　lumpiness　and　shape　of　the　rock　chips;　and　the　influence　of　penetration　on　the　cutter　force　was　given　as　well.　The　results　show　that　rock-breaking　efficiency　will　no　longer　be　improved　when　the　penetration　increases　to　a　certain　degree.　©　2016,　Editorial　Office　of　＂Modern　Tunnelling　Technology＂.　All　right　reserved.