〔Abstract〕 Objective To explore the function of miR-27 a-3 p on osteoblast differentiation of hDPSCs by targeting Yes-related protein 1(YAP1). Methods Human dental pulp stem cells(hDPSCs) were culturedin vitroand transfected with miR-27 a-3 p mimics(miR-27 a-3 p overexpression group), miR-27 a-3 p inhibitor(miR-27 a-3 p knock-down group) and miR-NC(control group), respectively. Real-time PCR(qRT-PCR) and Western blot were used to detect the effect of miR-27 a-3 p expression levels on YAP1. Bioinformatics predicted the target gene of miR-27 a-3 p which was then verified by dual luciferase reporter gene experiments. In addition, miR-27 a-3 p mimics and miR-NC were transfected into hDPSCs at the time stated. The expression of miR-27 a-3 p and the biochemical markers of bone formation of hDPSCs, such as bone morphogenetic protein-2(BMP-2) and runt-related transcription factor 2(RUNX2) and osteopontin(OPN), YAP1 mRNA was detected by qRT-PCR. Western blot was applied to detect the expression of BMP-2, RUNX2, OPN and YAP1 protein. The effect of miR-27 a-3 p or YAP1 on the proliferation of hDPSCs was analyzed by MTT assay. Results The expression of miR-27 a-3 p in the miR-27 a-3 p overexpression group increased in comparison with the control group(P<0.05), when that of YAP1 mRNA and protein was suppressed(P<0.05). Compared with control group, the expression of miR-27 a-3 p in miR-27 a-3 p knock-down group decreased(P<0.05) as that of YAP1 mRNA and protein increased(P<0.05). The target gene of miR-27 a-3 p was YAP1, which was predicted by bioinformatics and verified by dual luciferase reporter gene experiments(P<0.05). Overexpression of miR-27 a-3 p could promote expression of BMP-2, RUNX2, OPN mRNA and protein(P<0.05) while down-regulating the expression of YAP1 mRNA and protein. Overexpression of YAP1 could mitigate the effect of miR-27 a-3 p on proliferation of hDPSCs(P<0.05). Conclusion miR-27 a-3 p promotes osteogenic differentiation of hDPSCs, which may be related to the down-regulation of YAP1 by miR-27 a-3 p.