Abstract: A system model of the software reliability target assignment is first put forward. On the basis of method of assignment based on the system complexity factor, a method of engineering implementation is then used to solve for the degree of reliability for each subsystem under the condition that the whole system reliability is ensured. The degree of reliability found for each subsystem is finally tested by combing a practical command system. This method can be directly applied to the software reliability target assignment of military as well as non military systems.