AIM: To investigate the effects of modified Zhujing Pill on the mitochondrion structure and dynamin-related protein of retinal pigment epithelial cells(RPEs)in mice with form deprivation myopia.METHODS: 3-week-old C57BL/6J mice were randomly divided into control group, model group and Chinese medicine group, with 10 mice in each group. Myopia model of the right eye of mice was established by means of form deprivation in model and Chinese medicine groups. After 4wk, the Chinese medicine group were given intragastric administration of modified Zhujing Pill suspension 0.546g/(kg·d)(0.2mL/d)for 4wk, and same amount of saline was given to mice in other groups at the same time of modeling. The axial length and diopter of the right eye of the mouse were measured before and after the experiment by A-ultrasound and a strip retinoscope respectively. At the end of the experiment, the mitochondrial ultrastructure of RPEs was observed by transmission electron microscope. Western blot, and real-time fluorescent quantitative PCR(q-PCR)were used to detect quantitative and gene expression of mitofusin 1(MFN1), optic atrophy 1(OPA1), and dynamin-related protein 1(DRP1)in retinal tissues respectively.RESULTS: At the beginning of the experiment, there was no statistically significant difference in axial length and diopter of the right eye of the mouse in control, model and Chinese medicine groups(P>0.05). At the end of the experiment, compared with the control group, the mice in the model group and the Chinese medicine group had lower diopter and continuously prolonged axial length(all P<0.05), while the mice in the Chinese medicine group had significantly shorter axial length and higher diopter than the model group(all P<0.05). Western blot and q-PCR results showed that the relative expression of MFN1 and OPA1 decreased and DRP1 increased in both the model group and the Chinese medicine group compared with the control group(all P<0.05), and the relative expression of MFN1 and OPA1 increased in the Chinese medicine group compared with the model group(all P<0.05). The electron microscopic results showed that the mitochondria in the right retina of the mice were only mildly swollen in the Chinese medicine group, while the mitochondria in the model group were obviously swollen and disordered and empty.CONCLUSION: Modified Zhujing Pill could protect the retinal mitochondria by regulating the key proteins of mitochondrial dynamics(MFN1, OPA1, and DRP1), and it has a protective effect on the retina of axial myopic mice.