This　paper　investigates　the　rate-dependent　behavior　of　S690　high-strength　structural　steel　at　intermediate　strain　rates.　Experimental　tests　consisting　of　seven　groups　of　specimens　were　first　conducted,　and　stress-strain　curves　at　different　intermediate　strain　rates　were　obtained.　The　tests　indicated　that　the　strain　rate　had　an　obvious　influence　on　the　behavior　of　S690　steel,　i.e.,　both　the　yield　stress　and　tensile　strength　increased　remarkably　with　increasing　strain　rate.　The　test　results　were　then　used　to　determine　the　coefficients　of　two　commonly　used　rate-dependent　models,　i.e.,　the　Cowper-Symonds　(C-S)　model　and　the　Johnson-Cook　(J-C)　model.　A　new　modified　J-C　model　was　also　proposed　to　predict　the　true　stress-strain　behavior　of　S690　steel　at　intermediate　and　high　strain　rates　(up　to　4109　s(-1)).　The　accuracy　of　the　proposed　models　was　verified　by　comparing　them　with　test　results.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.