Roles based access control model CARBAC for cloud computing environment was proposed.Roles in the model include user roles and resources owner roles

the latter were called administrator roles.For the resources owner roles assigning the roles to the users

roles query algorithm in the hybrid hierarchies based on users’ access require was proposed.Through this algorithm

for the certain privileges set

this model could choose the least roles set to be assigned to the users.The simulation experiment indicates that for the mass user access

this algorithm can reduce the roles quan-tity

shorten the authorization procedure

and advance the system efficiency.