In　nature,　the　hammerhead　shark　possesses　a　special　rolled　swimming　motion　to　combat　the　effects　of　inborn　negative　buoyancy.　Inspired　by　this　natural　mechanism,　we　developed　a　novel　biomimetic　robotic　hammerhead　shark　to　explore　the　distinctive　rolled　swimming　motion　mode.　First,　a　scaled-down　robotic　prototype　is　constructed　based　on　the　morphological　characteristics　of　the　hammerhead　shark.　Second,　the　kinematics　and　dynamics　of　fish-like　swimming　are　built,　thereafter,　model　identification　and　validation　are　performed　to　improve　the　accuracy　of　the　robotic　model.　Furthermore,　the　physical　effects　of　the　long　dorsal　fin　and　the　rolling　state　on　swimming　performance　are　investigated　indepth　by　numerically　simulating　the　lift　and　drag　forces　over　different　fin　surfaces　and　the　dynamic　torque　of　the　body.　Finally,　extensive　aquatic　experiments　demonstrate　the　remarkable　improvements　on　locomotion　performance　and　propulsive　efficiency　of　the　robotic　hammerhead　shark　by　the　proposed　rolled　motion.　The　obtained　results　provide　a　new　solution　for　the　long　voyage　of　high-load　robotic　fish　system.