Objective To observe the dynamic changes in protein expression of the orphan nuclear receptor related factor 1(Nurr1) as well as its correlation with proliferating cell nuclear antigen(PCNA) in the developing rat brain, and to investigate the significance of Nurr1 in the differentiation and migration of neural cells. Methods Paraffinembedded sections, immunohistochemistry, double labeling immunohistochemical methods were adopted. Results Nurr1 was expressed in small quantities in the cells surrounding the lateral ventricle. Along with the maturing of the cells, the positive expression increased apparently and differentiated and migrated to the distant sites from the lateral ventricle. In postnatal rats, the positive cells surrounding the lateral ventricle decreased remarkably. High levels of the expression was found in the cerebral cortex on the postnatal day 1-5, then along with the maturing of the cells, the positive expression decreased obviously. Positive cells were rare in matured cerebral cortex. The comparative observation against PCNA showed that the two were expressed at different sites and in different cells. Nurr1 was mainly expressed in differentiated and migrated immature cells, but not in proliferating cells. Conclusion It implies that Nurr1 may play a regulatory role in the differentiation, migration and maturation of the rat neural cells.