Abstract:To improve the security of private cloud platform and apply cloud platform to aerospace area,this paper made deep research on the security mechanism in cloud platform. In this paper,we analysed the Kerberos released by apache, then we introduce the principle of Kerberos and the workflow of Kerberos in Hadoop,we point out that Kerberos have some defects, first,Kerberos is too dependent on KDC,second,Kerberos use symmetric cryptographic communication,third,the communication between client and HDFS uses plaintext. So we designed a new authenticated scheme based on PKI which can solve those problems in Kerberos,and we practical apply it in Hadoop platform .