Aim: To study the neurotoxicity of human full-length alpha-synuclein (α-SYN) to the dopaminergic neurons in the substantia nigra of SD rats. Methods: α-synuclein was expressed with prokaryotic expression vector and identified by using Western blot. A total of male 30 SD rats were divided randomly into three groups: α-SYN, 6-hydroxydopamine (6-OHDA) and α-SYN + 6-OHDA steretaxically were injected into the right substantia nigra of SD rats respectively, and saline of the same volume was injected into the left substantia nigra in all the groups. The dopamine of striatum and the dopaminergic neurons of substantia nigra were quantitatively analyzed. Results: Injection of 6-OHDA and α-SYN + 6-OHDA decreased the quantity of dopamine in striatum to 36.98% and 21.79% of that in the control sides, respectively, and meanwhile the number of dopaminergic neurons in substantia nigra was decreased to 30.81% and 28.05%. However, α-synuclein injection had no significant effect on the quantity of dopamine in striatum and the number of dopaminergic neurons in substantia nigra. Conclusion: There is no evidence for the obvious neurotoxicity of recombinant human α-SYN to the dopaminergic neurons of substantia nigra in SD rats.