Abstract： Objective To observe the therapeutic effect of microencapsulated human retinal pigment epithelial (RPE) cell transplantation into the striatum in a rat model of Parkinson' disease (PD). Methods Cultured RPE cells were microencapsulated by alginate-polylysine-alginate (APA) using a high voltage electrostatic system. The Parkinsonian rats were divided into 4 groups, namely the model group, RPE group, APA group and RPE-APA group, and in the latter 3 groups, RPE cells, empty APA microcapsules and APA-capsulated RPE cells, respectively, were transplanted into the right striatum of the rats via stereotactic surgery. After the transplantation, the changes in apomorphine-induced rotation of the rats were investigated and the striatum DA contents were measured with high-performance liquid chromatography with electrochemical detection. Results TThe rotation of the rats in RPE-APA group was reduced by 51.48%, showing significant difference from that in the model control group 4 weeks after the transplantation (P<0.05). At 8 weeks after the transplantation, apomorphine-induced rotation in the RPE-APA group showed further significant reduction by 54.43% (P<0.05). The changes of DA contents in the striatum after transplantation were consistent with the changes in the rotation behavior of the rats. Conclusions Microencapsulated human RPE cell transplantation is a promising approach for the treatment of PD.