Usually,　traditional　poly　(ionic　liquid)s　are　prepared　to　nanoparticles　with　high　surface　areas　for　achieving　a　quasi-homogeneous　reaction　system.　In　this　work,　a　novel　poly　(ionic　liquid)　P(VB-VS)HSO4,　synthesized　by　simply　using　ionic　liquids　immobilized　on　the　1-vinylimidazole-based　crosslinked　copolymer　microsphere,　was　used　as　heterogeneous　catalyst　for　transesterification　of　a　novel　non-edible　feedstock　soapberry　oil　to　biodiesel.　The　structure,　thermal　stability　and　wetting　property　characteristics　of　the　crosslinked　copolymer　microsphere　particles　and　poly　(ionic　liquid)　microspheres　were　investigated.　The　results　indicated　that　ionic　liquids　were　successfully　functionalized　on　crosslinked　copolymer　microsphere,　and　P(VB-VS)HSO4　possessed　high　surface　areas　(100.1　m2/g),　abundant　meso-macropores　(with　diameter　of　∼18.9　nm),　good　mechanical　strength　(81　N)　and　superior　thermal　stability.　Benefiting　from　the　unique　structure　features,　these　poly　(ionic　liquid)　microspheres　manifested　excellent　catalytic　performance　for　transesterification　of　soapberry　oil　with　methanol.　A　maximum　fatty　acid　methyl　esters　(FAMEs)　yield　of　95.2%　could　be　obtained　under　the　response　surface　methodology　(RSM)　optimized　conditions　of　8.0　h　reaction　time,　29.1　methanol　to　oil　molar　ratio,　and　8.7　wt%　catalyst　amount.　Impressively,　it　was　also　efficient　for　the　esterification　of　oleic　acid,　giving　methyl　oleate　yield　of　97.5%.　Catalytic　tests　exhibited　that　P(VB-VS)HSO4　presented　high　catalytic　activity　and　good　reusability　in　comparison　with　traditional　acid　catalysts.　The　main　physicochemical　of　the　obtained　soapberry　biodiesel　met　the　biodiesel　standard　ASTM　D6751.　Therefore,　this　work　provides　a　cheap　and　facile　route　to　the　synthesis　of　size-controlled　poly　(ionic　liquid)　microspheres　(the　diameter　of　the　catalyst　was　about　500　μm)　for　catalyzing　the　production　of　clean　biofuels.　©　2017　Elsevier　Ltd