To　analyze　the　causes　of　the　great　rotation　angles　occurring　on　the　skewed　multi-span　simply-supported　girder　bridges　under　the　strong　earthquake　and　the　influences　of　the　skew　degrees　and　width-to-span　ratios　on　the　rotation　angles　of　the　decks　of　the　bridges,　an　assembly　prestressed　concrete　box　girder　bridge　was　taken　as　the　example,　the　software　OpenSees　was　used　to　establish　the　dynamic　calculation　models　for　the　bridges　(respectively　with　two　spans　and　three　spans)　and　the　time-history　analysis　method　was　used　to　study　the　influences　of　the　skew　degrees,　width-to-span　ratios　and　pounding　action　on　the　rotation　of　the　decks.　The　results　of　the　study　indicate　that　the　occurrence　of　the　great　rotation　angle　on　the　deck　of　the　skewed　two-span　simply-supported　girder　bridge　under　the　strong　earthquake　is　mainly　caused　by　the　eccentric　effect　of　the　structure.　When　the　unilateral　longitudinal　pounding　between　the　adjacent　decks　is　considered　and　the　parameter　related　to　the　skew　degrees　and　width-to-span　ratios　η1,　the　moment　will　intensify　the　rotation　of　one　of　the　decks　and　will　restrain　that　of　the　other.　The　rotation　of　the　deck　of　the　central　span　of　the　skewed　three-span　simply-supported　girder　bridge　under　the　strong　earthquake　is　mainly　caused　by　the　longitudinal　pounding　among　the　adjacent　decks.　When　skew　degree　is　less　than　45°,　if　the　unilateral　longitudinal　pounding　of　the　decks　is　considered　only,　the　maximum　rotation　angle　of　the　deck　of　the　central　span　increases　with　the　increase　of　the　η　and　if　the　bilateral　longitudinal　pounding　is　considered,　the　maximum　rotation　angle　of　the　deck　exhibits　the　tendency　of　increasing　first　and　decreasing　then　with　the　increase　of　the　η.　©　2017,　Journal　Press,　China　Railway　Bridge　Science.　All　right　reserved.