Alzheimer's disease (AD) is a neurodegenerative disorder which mainly affects elderly population. MicroRNAs (miRNA) are small RNA molecules that fine-tune gene expression at posttranscriptional level and exert important functions in AD. MicroRNA-124 (miR-124) is a kind of miRNA abundantly expressed in the central nervous system. It is highly conserved from Caenorhabditis elegans to humans. However, its function in AD is still elusive. In this study, we found miR-124 was significantly down-regulated in AD flies. miR-124 mutant flies showed impaired climbing ability and shortened lifespan. In contrast, miR-124 expression rescued locomotive defects of AD flies. Using microarray analysis to test gene expression profiles of miR-124 mutant flies, we found that Notch signaling pathway was potentially targeted by miR-124. Further experiments showed that miR-124 regulated Notch ligand Delta expression by acting on specific site of Delta 3`UTR. In addition, reduced Delta expression by RNA interference extended lifespan and ameliorated learning defects of AD Drosophila. Notch inhibitor DAPT could also alleviate AD phenotypes, which confirmed our findings. In conclusion, our study indicates that miR-124 plays neuroprotective roles in AD Drosophila by targeting Delta in Notch signaling pathway, which helps further our understanding of miRNAs in the molecular pathology of AD.