Objective To observe the clinical effect of umbilical cord mesenchymal stem cells（UC-MSC） in the treatment of spinocerebellar ataxia（SCA） and multiple system atrophy-cerebellar type（MSA-C） by intrathecal injection.Methods From Oct 2009 to Sep 2010,14 cases with SCA and 10 cases of MSA-C were given UC-MSC by weekly intrathecal injection at a dose of 1×106 cells/kg for four times as a course.All the patients received 1 course of treatment except 3 cases received 2 cycles.The movement ability and the quality of daily life were evaluated with the International Cooperative Ataxia Rating Scale（ICARS） and Activity of Daily Living Scale（ADL） and the scores were compared with those before the treatment.Results The results showed that the scores were significantly decreased 1 month after treatment（P<0.01）.The symptoms,including unstable walking and standing,slow movement,upper limb fine motor disorders,writing difficulties and dysarthria,were greatly improved except one patient who had no response.The observed side effects included dizziness（4 patients）,back pains（2 cases） and headache（1 case）,which disappeared within 1-3 days.Conclusion UC-MSC implantation is safe,and able to ameliorate clinical symptoms and improve life quality of SCA and MSA-C patients to some extent as well.