Abstract: The mature embryos of a Japonica rice, Guanglingxiangnuo, were used for the study on optimization of Agrobacterium-mediated transformation. Several factors affecting the transformation were investigated and a suitable transformation system was set up. For this transformation system, the HRM medium, based on the MS medium, was suitable for inducing callus from rice mature embryos. The suitable time span of initial culture in this medium was 7~8 days before co-culturing with Agrobacterium and suitable medium for selection was CC medium. Using this transformation system, the Metr gene was introduced into Guanglingxiangnuo, and many transgenic plants were obtained. Most of these transgenic rice plants were confirmed by PCR technique and basta resistance, indicating the T-DNA had been integrated into the genome of transgenic rice plants.