Liquid-liquid　equilibrium　(LLE)　data　of　the　water　+sec-butyl　alcohol　+　sec-butyl　acetate　ternary　system　were　measured　at　303.15　K,　323.15　K,　343.15　K　and　353.15　K　under　atmospheric　pressure.　The　active　coefficients　in　the　LLE　equations　were　calculated　by　the　NRTL　and　UNIQUAC　models,　and　the　calculated　LLE　data　of　water　+　sec-butyl　alcohol　+　sec-butyl　acetate　ternary　system　were　compared　with　the　experimental　data.　Based　on　the　NRTL　and　UNIQUAC　models,　the　calculated　equilibrium　compositions　of　the　studied　ternary　system　are　in　good　agreement　with　the　experimental　data.