Freak　wave　is　an　extreme　sea　state　with　unexpected　and　huge　wave　height,　which　becomes　a　potential　risk　for　lay　barge　and　offshore　pipeline　during　deepwater　installation.　In　order　to　investigate　the　dynamic　responses　of　deepwater　S-lay　pipeline　induced　by　freak　waves,　this　study　developed　a　comprehensive　numerical　model　with　the　particular　consideration　of　the　freak　wave　effect.　An　enhanced　superposition　method　of　combined　transient　wave　trains　and　random　wave　trains　was　presented,　and　a　series　of　freak　wave　trains　were　generated.　The　induced　pipelay　vessel　motions　were　simulated　by　the　use　of　displacement　response　amplitude　operators　(RAOs).　The　pipe-stinger　roller　interactions　in　the　overbend　and　the　cyclic　contacts　between　the　pipeline　and　seabed　soil　in　the　touchdown　zone　(TDZ)　were　fully　taken　into　consideration.　The　developed　S-lay　model　was　subsequently　utilized　to　calculate　the　dynamic　responses　of　the　pipelay　vessel　and　offshore　pipeline　under　random　waves　and　freak　waves　for　a　comparison.　The　results　illustrated　the　remarkable　influence　of　freak　waves　on　the　systematic　behaviors　of　deepwater　S-laying　pipeline,　which　offer　a　significant　theoretical　basis　for　the　pipe　structure　design　and　pipelay　operation　safety.