The invention belongs to the technical field of computer software security, and discloses a computer software authority distribution method and a system, and the method comprises the steps: establishing a tree-shaped interface element model for interface elements of software according to the dependence relation among all interface elements, and binding an API interface depended by each interface element to a node of the model; associating a plurality of nodes of non-tree root nodes in the interface element model to a certain role when the role is authorized; deriving an indirect permission node according to the direct permission node associated with the role and associating the indirect permission node to the role; wherein a union set of all direct permission nodes and indirect permissionnodes associated with the role is used as an interface element permission of the role; generating API interface permission according to all the direct permission nodes and indirect permission nodes associated with the role; when a request of using the software by the user is received, only the interface elements which the user has the right to see are displayed according to the interface element permission of the user role; and when a request is initiated to the server, performing authentication by the server according to the API interface permission of the user role.