Developing　flexible　sensors　and　actuators　is　of　paramount　importance　for　wearable　devices　and　systems.　In　this　research,　we　developed　a　simple　and　facile　technique　to　construct　flexible　piezoresistive　sensors　from　polydimethylsiloxane　films　with　ridge-like　surface　structures　and　laser-induced　porous　graphene.　Using　a　replication　strategy,　we　prepared　the　ridge-like　surface　structures　from　sandpapers.　The　piezoresistive　sensors　exhibit　excellent　sensitivity　with　a　response　time　of　less　than　50　ms　and　long-term　cyclic　stability　under　mechanical　loading.　The　smallest　weight　they　can　sense　is　similar　to　96　mg.　We　demonstrated　applications　of　the　piezoresistive　sensors　in　the　sensing　of　bio-related　activities,　including　muscle　contraction,　finger　flexion,　wrist　flexion,　elbow　bending,　knee　bending,　swallowing,　respiration,　sounds,　and　pulses.