Exogenous microRNA-144 (miR-144) is considered as a potential biological drug for gastric cancer because of its biological activity to inhibit the epithelial-mesenchymal transition (EMT). However, the specific molecular mechanisms have not been fully revealed. In addition, their vulnerability to degradation by RNA enzymes in the blood limits their bioavailability. In this paper, a polyamidoamine (PAMAM)-wrapped miR-144 (PAMAM/miR-144) is prepared as a nanocarrier system to protect miR-144 from nuclease degradation. The PAMAM/miR-144 nanocarrier system achieves the optimal antitumor activity against gastric cancer migration and reduce mTOR protein expression by transferring miR-144 into human gastric cancer HGC-27 cells. At the same time, the PAMAM/miR-144 nanocarrier system significantly decreases the EMT via targeting mTOR signal pathway in HGC-27 cells and noticeably inhibited the growth of subcutaneous gastric cancer xenografts in nude mice. PAMAM/miR-144 nanocarrier system has effectively improved the bioavailability of miR-144, thus providing a promising combination modality for anticancer therapy.