In　order　to　obtain　the　basic　data　for　improving　the　hydrolysis　conversion　ratio　of　the　methyl　acetate　in　the　catalytic　distillation　process,　the　LLE　(Liquid-Liquid　Equilibrium)　data　for　methyl　acetate-water-acetic　acid　ternary　system　and　methyl　acetate-methanol-water-acetic　acid　quaternary　system　were　determined　at　20,　30,　40　and　50°C　under　atmospheric　pressure.　Both　NRTL　and　UNIQUAC　models　were　adopted　to　correlate　the　liquid-liquid　equilibrium　data　which　were　obtained　from　experimental　measurement.　The　model　parameters　were　estimated　by　the　simplex　method.　The　active　coefficients　in　the　LLE　equations　were　calculated　respectively　by　the　NRTL　and　UNIQUAC　models,　and　the　calculated　LLE　data　of　methyl　acetate-　methanol-water-acetic　acid　quaternary　system　were　compared　with　the　experimental　data.　The　results　show　that　both　the　calculated　data　based　on　the　NRTL　and　UNIQUAC　models　are　in　good　agreement　with　the　experimental　data.　The　total　mean　absolute　deviations　of　NRTL　and　UNIQUAC　models　are　0.00114　and　0.00133,　respectively,　and　the　mean　relative　deviations　of　them　are　3.025%　and　3.839%,　respectively.