The invention provides a role permission dynamic control method and system. The method comprises: according to roles, obtaining permissions of modules corresponding to the roles; modifying and storing the permissions of the modules, wherein the process of modifying the permissions of the modules comprises the assignment of the permissions of the modules according to power series of 2 and the selection of the assigned permissions of the modules; summating permission values of the selected permissions and storing an obtained sum value in a preset corresponding relationship table, wherein the corresponding relationship table has a corresponding relationship among the roles, the modules and the permissions; according to the roles, obtaining permission values of the permissions of the modules corresponding to the roles; and performing AND operation bit-by-bit on the permission values of the permissions of the modules and the sum value stored in the corresponding relationship table, and when a value obtained by the operation is the same as the permission value of a permission of the modules, loading the permission of the module, corresponding to the permission value. By utilizing the role permission dynamic control method and system, the function of modifying the permissions of the user roles in the modules in real time can be achieved.