Objective To establish a stably overexpressing miR?31 transgenic mouse and detect the expression of miR?31 in the organs and tissues, and to provide qualified tool mice with overexpression of miR-31 in vivo. Methods The miR-31 overexpression vector was constructed by Gateway cloning technology. The vector was injected into fertilized ovum by DNA microinjection technology, then transferred to the pseudopregnant mice and waited for eutocia. Newborn mouse tail DNA was extracted and PCR and agarose gel electrophoresis were performed to identify the positive miR-31 transgenic mice. microRNA was extracted from the organs and tissues of miR-31 transgenic mice and the expression of miR-31 was detected by RT-PCR. The expression of Nestin and number of neural stem cells in the nervous system were compared in the positive and WT mice. Results The miR-31 transgenic mice were constructed successfully and bred more than 14 generations in barrier environment. Expression of miR-31 was increased in major organs and tissues. The expression of Nestin and the number of neural stem cells in the positive mice were higher than those in the wild type mice. Conclusions MiR-31 overexpressing transgenic mice are constructed by Gateway cloning technology and the expression of miR-31 is stable in subsequent generations. The number of neural stem cells in the nervous system is higher than that in wild-type mice. The miR-31 overexpressing transgenic mice can be a good tool for experimental research of the function of overexpressed miR-31 in vivo and the treatment of nervous system diseases.