Based　on　the　principle　that　the　scale　of　near-wall　vortices　could　be　enlarged　in　the　drag-reducing　surfactant　solution　and　the　longitudinal　microgrooves　could　reduce　drag　by　restricting　the　motions　of　near-wall　streamwise　vortices,　the　possible　complementary　mechanism　of　drag　reduction　with　surfactant　and　microgrooves　was　proposed,　and　their　collaborative　drag-reducing　performance　was　verified　by　experiments.　The　collaborative　drag-reducing　performances　of　0.22　mmol/L　CTAC/NaSal　surfactant　solution　in　longitudinal　microgroove　channels　with　different　sizes　at　different　temperatures　were　investigated.　It　is　found　that　the　drag　reduction　performance　of　0.22　mmol/L　CTAC/NaSal　solution　can　be　enhanced　by　microgrooves　at　20,　the　maximum　drag　reduction　rate　increases　from　66%　in　smooth　channel　to　71%　in　G1　channel　and　74%　in　G2　channel,　respectively.　The　critical　Reynolds　number　and　critical　temperature　of　drag-reducing　solution　in　G1　channel　are　lower　than　that　in　G2　channel,　but　they　are　almost　the　same　for　G2　channel　and　smooth　channel.　The　drag-reducing　size　of　microgroove　could　be　enlarged　in　the　drag-reducing　solution.　The　collaborative　drag-reducing　mechanism　of　surfactant　and　microgroove　might　be　that　the　scale　of　near-wall　vortices　is　enlarged　in　surfactant　solutions,　resulting　in　that　microgrooves　restrict　more　near-wall　streamwise　vortices　and　maintain　the　drag　reduction　performance　at　higher　Reynolds　number.　©　2019,　Editorial　Office　of　Journal　of　Xi＇an　Jiaotong　University.　All　right　reserved.