With the rapid development of computer technology,cloud-based services have become a hot topic.They not only provide users with convenience,but also bring many security issues,such as data sharing and privacy issue.In this paper,we present an access control system with privilege separation based on privacy protection (PS-ACS).In the PS-ACS scheme,we divide users into private domain (PRD) and public domain (PUD) logically.In PRD,to achieve read access permission and write access permission,we adopt the Key-Aggregate Encryption (KAE) and the Improved Attribute-based Signature (IABS) respectively.In PUD,we construct a new multi-authority ciphertext policy attribute-based encryption (CP-ABE) scheme with efficient decryption to avoid the issues of single point of failure and complicated key distribution,and design an efficient attribute revocation method for it.The analysis and simulation result show that our scheme is fea sible and superior to protect users’ privacy in cloud-based services.