Objective To investigate the expression and role of Huntingtin-associated protein-1 (HAP-1) in the process of valproate acid (VPA) inducing neural stem cells (NSCs) into neurons.    Methods The hippocampus NSCs of SD rats were isolated and cultured, Real-time PCR and Western blotting were used to detect HAP-1 mRNA and protein expression at day 0, day 1, day 3 and day 5 during the induction of VPA on NSCs differentiation into neurons; Real-time PCR was used to detect the expression level of HAP-1 mRNA in multiple tissues of adult SD rats, as well as NSCs, neurons and astrocytes. After applying small interfering RNA technology to down-regulate the expression of HAP-1 mRNA in NSCs, Real-time PCR was used to detect the mRNA expression levels of neuron-specific molecules stathmin-2 (Stmn-2), neuronal differentiation-1 (Neurod-1), microtubule-associated protein-2 (Map-2) and synapsin-1 (Syn-1), and Western blotting was used to detect the protein expression levels of neuron-specific marker β-tubulinⅢ（Tuj-1）. Immunofluorescence was used to detect the proportion of NSCs differentiated into Tuj-1 positive neurons, and to observe the development of neurons.    Results At day 1 and day 3 after VPA treatment, the expression of HAP-1 mRNA and protein in the VPA group was significantly up-regulated; HAP-1 mRNA was predominantly expressed in the hippocampus, and its expression was higher in neurons, followed by NSCs, and minimally in astrocytes. After down-regulating HAP-1 with small interference technology, the proportion of NSCs differentiated into Tuj-1 positive neurons reduced, and neuron development became worse.    Conclusion VPA may promote the differentiation of NSCs into neurons by up-regulating HAP-1 expression.