Abstract: Fine-grained software rejuvenation,that is partial restart technique,can further reduce the rejuvenation cost and improve the system availability.Before formulating the fine-grained software rejuvenation policy,the objects that can restart safely must be determined and the restart tree of computing system must be built.Therefore,based on the typical software architecture and the control,invoke and data access connection among modules,this paper studies the relation between the module-module coupling and the restart dependence,defines the restart depen-(dence)and its degree,and obtains the restart reachable set and restart group of each module.Taking the restart groups as the restart objects of rejuvenation policy,the restart tree can be built according to the wastage degree of system resource incurred by modules.Finally,the software rejuvenation policy is determined,and the implementation process of the policy is modelled by finite-state automaton.