The　circadian　clock　is　a　rhythmic　oscillator　driving　various　physiological　and　behavioral　processes　that　adapt　to　daily　environmental　changes.　MicroRNAs　(miRNAs)　are　a　class　of　small　non-coding　RNAs　that　play　an　important　role　in　post-transcriptional　regulation.　Although　recent　work　has　demonstrated　that　miRNAs　are　involved　in　development　and　disease,　their　function　in　the　adult　circadian　locomotor　rhythm　still　needs　to　be　extensively　characterized.　In　this　study,　we　identified　the　miR-263a　as　an　important　regulator　of　Drosophila　circadian　locomotor　rhythm,　with　miR-263a　expression　in　LNv　clock　neurons.　The　overexpression　of　miR-263a　in　clock　neurons　lengthens　the　circadian　period,　while　its　mutant　Bereft(24)　shortens　the　circadian　period.　In　addition,　downregulation　of　miR-263a　also　dramatically　attenuates　the　morning　activity　peak　as　well　as　circadian　rhythm　robustness.　Moreover,　slo　and　homer　are　identified　as　the　potential　targets　of　the　miR-263a.　Together,　these　results　establish　that　the　miR-263a　is　an　important　regulator　of　circadian　locomotor　rhythm.