With　the　combination　of　molecular　simulation　and　relevant　experiments,　the　efficient　Brønsted-Lewis　acidic　ionic　liquid　(IL)　was　designed　and　synthesized　for　biodiesel　production　from　soapberry　oil.　In　molecular　simulation,　4-methylthiazole　(MT)　is　proved　to　be　the　best　matrix　for　IL　preparation　via　electrostatic　potential　analysis　and　proton　affinity　analysis,　and　it　also　is　verified　by　experiments.　In　orthogonal　experiment,　the　relationship　in　catalytic　activity　between　Brønsted-Lewis　acidic　IL　and　corresponding　materials　(Brønsted　acidic　IL　and　metal　chloride)　was　revealed.　Meanwhile,　[Ps-MTH][CF3SO3]　and　FeCl3　are　verified　as　the　best　materials　for　preparation　of　Brønsted-Lewis　acidic　IL,　and　[Ps-MTH][CF3SO3]-FeCl3(x　=　0.65)　is　determined　as　the　most　efficient　catalyst　in　the　end.　The　Lewis　acidity,　Brønsted　acidity　and　interaction　of　[Ps-MTH][CF3SO3]　and　FeCl3　in　[Ps-MTH][CF3SO3]-FeCl3(x　=　0.65)　were　characterized　by　FT-IR.　And　the　catalytic　mechanism　of　transesterification　catalyzed　by　prepared　IL　was　clarified.　In　order　to　maximize　the　biodiesel　yield,　optimization　of　process　variables　was　conducted　using　Box-Behnken　response　surface　methodology.　The　97.04%　of　high　biodiesel　yield　is　obtained　under　the　optimum　conditions:　reaction　temperature　was　127　°C,　molar　ratio　(methanol　to　soapberry　oil)　was　27.96:1,　catalyst　amount　was　3.06　mmol　and　reaction　time　was　8　h.　Furthermore,　[Ps-MTH][CF3SO3]-FeCl3(x　=　0.65)　presents　good　catalytic　activity　in　different　transesterification　for　biodiesel　production.　And　its　catalytic　activity　decreases　from　97.04%　to　93.59%　after　being　used　for　5　times,　which　reflects　good　reusability.　The　main　properties　of　soapberry　biodiesel　were　also　measured　and　compared　to　the　ASTM　D6751　standard.　©　2018　Elsevier　Ltd