Two　different　fish　oil　preparations,　namely　triglycerides　and　ethyl　esters　containing,　respectively,　30.02%　and　74.38%　of　omega-3　fatty　acids,　were　employed　as　the　substrates　for　transesterification.　Catalyzed　by　immobilized　lipase　using　imidazolium-based　ionic　liquid　systems,　the　total　content　of　eicosapentaenoic　acid　(EPA)　and　docosahexaenoic　acid　(DHA)　in　the　resulting　triglyceride　reached　63.60%　when　4%　hydrophobic　ionic　liquid　was　used,　which　was　11.74%　higher　than　that　of　the　triglyceride　produced　in　a　solvent-free　reaction　system.　The　activation　energy　of　the　product　(triglyceride-type　fish　oil)　was　173.64　KJ　mol　−1　,　which　was　not　significantly　different　from　that　of　the　commercial　ethyl　ester-type　fish　oil,　so　were　the　other　thermal　oxidative　kinetic　parameters.　The　kinetic　parameters　depicting　the　thermal　and　oxidative　stability　of　the　fish　oil　product　provide　the　basis　for　industrial　processing,　storage,　and　applications.　©　2018　The　Authors.　Food　Science　&　Nutrition　published　by　Wiley　Periodicals,　Inc.