The　mode　of　outsourcing　brings　about　new　challenges　for　data　security　and　access　control　in　cloud　computing.　Ciphertext-Policy　Attribute-based　Encryption　(CP-ABE)　is　considered　to　be　a　powerful　tool　for　protecting　data　confidentiality　in　cloud　storage　system.　Due　to　the　large　scale　of　cloud,　there　are　many　independent　domains.　It　is　impossible　for　a　single　authority　to　issue　attributes　to　all　of　the　users.　In　addition,　single　authority　could　be　the　bottleneck　of　system.　Attribute　revocation　has　always　been　the　primary　difficulty　in　ABE.　In　this　paper,　we　propose　a　multi-authority　cloud　access　scheme　with　mixed　access　structure　to　support　universal　attribute　and　more　flexible　access　control　in　multi-authority　cloud　storage　system.　After　adding　owner-defined　attribute　to　traditional　access　structure,　owner　can　decide　which　user　has　the　right　to　access　data.　Two　kinds　of　revocation　methods　can　provide　real-time　privilege　updating　in　multi-authority　system.　Detailed　security　analysis　shows　that　the　proposed　MMACS　scheme　meets　the　security　requirements　under　existing　security　models.　Performance　evaluation　also　demonstrates　its　highly　efficient　in　attribute　revocation.　©　2014　IEEE.